Wizard/Arcane Trickster/Eldritch Knight Spell Learning Question

[SociopathFriend]

So I'm plotting out a build for my 5e Necromancer running through the Mad Mage Dungeon. We're several months in mind you but I was bored at work and was thinking about it.

Spoiler: Stat block for those interested

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Current Stats:
Level 8 Necromancy Wizard
HP 40/40
Str 11
Dex 14
Con 14
Int 20
Wis 10
Cha 10

Items:
Wand of Web, Periapt of Wound Closure, Good Luck Stone, Bag of Holding (Tends to hold x4 Animated Dead)

I plan to continue leveling as a Wizard to next get Resilience (Constitution) followed by maxing my Con but past level 16 I don't see a great appeal of the Wizard class features Spell Mastery and Signature Spell.
So while I'm debating multiclassing to Fighter or Rogue and their spellcasting subclasses- I'm not sure I understand how gaining spells works.

The Multiclassing states you should treat spells learned as though you're only leveled in that class.

Spells Known and Prepared. You determine what spells you know and can prepare for each class individually, as if you were a single-classed member of that class. If you are a ranger 4/wizard 3, for example, you know three 1st-level ranger spells based on your levels in the ranger class.

Eldritch Knight states:

You know three 1st-level wizard spells of your choice, two of which you must choose from the abjuration and evocation spells on the wizard spell list.
The Spells Known column of the Eldritch Knight Spellcasting table shows when you learn more wizard spells of 1st level or higher. Each of these spells must be an abjuration or evocation spell of your choice, and must be of a level for which you have spell slots. For instance, when you reach 7th level in this class, you can learn one new spell of 1st or 2nd level.
The spells you learn at 8th, 14th, and 20th level can come from any school of magic.
Whenever you gain a level in this class, you can replace one of the wizard spells you know with another spell of your choice from the wizard spell list. The new spell must be of a level for which you have spell slots, and it must be an abjuration or evocation spell, unless you're replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic.

Arcane Trickster states:

You know three 1st-level wizard spells of your choice, two of which you must choose from the enchantment and illusion spells on the wizard spell list.
The Spells Known column of the Arcane Trickster Spellcasting table shows when you learn more wizard spells of 1st level or higher. Each of these spells must be an enchantment or illusion spell of your choice, and must be of a level for which you have spell slots. For instance, when you reach 7th level in this class, you can learn one new spell of 1st or 2nd level.
The spells you learn at 8th, 14th, and 20th level can come from any school of magic.
Whenever you gain a level in this class, you can replace one of the wizard spells you know with another spell of your choice from the wizard spell list. The new spell must be of a level for which you have spell slots, and it must be an enchantment or illusion spell, unless you're replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic.

My question is how does this work if you've already existing Wizard spell slots from being a level 8-16 Wizard?
Do you gain the three 1st level spells like each class states and then more levels allow you to learn spells as though you're single-classed into them? So possessing no better spell slots to get any higher spells?
OR
Do you gain the three 1st level spells like each class states then more levels allow you to learn spells using your full available multiclassed spell slots? So even though you've only say 4 levels in the not-Wizard subclass you can still pick up say a 3rd or 4th level spell?
OR
Are the three 1st level spells even required to be 1st level or is just assumed you won't have any higher slots available because multiclassing isn't inherently factored into the classes?

I'm not sure whether I want to stay Wizard or multiclass 4 levels into either of the other classes but it would help if I understood how multiclassing into them affects my potential spells learned. Obviously as a Wizard I can learn then via other methods than leveling but I'm trying to figure out how it works to help make the decision.
As a Necromancer specialist I certainly see the appeal of being able to take hits as well as dish them out (Fighter) but a lot of my current spells aren't all that based around blowing stuff up so I can certainly also see the appeal of never getting into a straight fight in the first place (Rogue).

[Anymage]

EKs and ATs are separate spellcasting classes that just happen to use the wizard list. An EK6/Wiz9 will know two cantrips and four first level spells from the EK side, plus four cantrips and (9+Int mod) wizard spells across all levels that a ninth level wizard could prepare. Note that despite this being a fifteenth level character with the spell slots of an eleventh level character, they can't prepare higher than fifth level spells on their wizard side since that's as high as a ninth level wizard could go. As a consequence of this, having seventeen levels in a caster class is very nice, with the last three being less critical.

The multiclassing rules explain how to figure out how many spells of each level you have. Multiclass casters will often wind up having slots for levels they don't know spells for, and will use them for upcasting. Note that spells can be upcast to the highest level slot possible, regardless of the class level; a Wiz19/Clr1 could still cast Cure Wounds from a ninth level slot, if he really wanted to.

I'll note that in addition to 17 being an important cutoff, Wiz18 is nothing to sneeze at. Spell Mastery has some great picks; at-will Shield and Misty Step can be incredibly useful. After that Ftr2 for armor and Action Surge is nice, but the question is when you want to pull the trigger on those levels. 5e is nice in that for most of your leveling career, there is a compelling reason to continue in your existing class.

[bid]

My question is how does this work if you've already existing Wizard spell slots from being a level 8-16 Wizard?
Do you gain the three 1st level spells like each class states and then more levels allow you to learn spells as though you're single-classed into them? So possessing no better spell slots to get any higher spells?
OR
Do you gain the three 1st level spells like each class states then more levels allow you to learn spells using your full available multiclassed spell slots? So even though you've only say 4 levels in the not-Wizard subclass you can still pick up say a 3rd or 4th level spell?
OR
Are the three 1st level spells even required to be 1st level or is just assumed you won't have any higher slots available because multiclassing isn't inherently factored into the classes?

Anything in the Classes chapter uses the class level, as if the other classes levels didn't exist. If you are a wizard 8 and you MC into another class, you are still a wizard 8 for all the wizard features. It doesn't matter if you are a character level 8 pure wizard or character level 13 because you MC into EK 5. You are still only level 8 for all wizard features.
Each class is handled separately and independently for the classes' features.

Think of it this way:
- Could a wizard 16 / cleric 1 learn true resurrection?
No absolutely not, a cleric 1 doesn't have a 9th slot.
- Could a wizard 16 / cleric 1 learn wish?
No absolutely not, a wizard 16 doesn't have a 9th slot.

[SociopathFriend]

EKs and ATs are separate spellcasting classes that just happen to use the wizard list.

Ah- that's basically the answer to that question then. That was the only part really confusing me.

I'll note that in addition to 17 being an important cutoff, Wiz18 is nothing to sneeze at. Spell Mastery has some great picks; at-will Shield and Misty Step can be incredibly useful. After that Ftr2 for armor and Action Surge is nice, but the question is when you want to pull the trigger on those levels. 5e is nice in that for most of your leveling career, there is a compelling reason to continue in your existing class.

Mainly I just want to be harder to kill.
I've never felt so squishy as "average hp" Wizard in all of 5e. Just last session a Warlock walked through a gate and got slugged with like 50-60ish damage just for existing. That'd drop me with no questions asked and my spells won't do me any good then.
And we'd only just recently finished fighting Drow Elite Warriors who also (prior to my level-up to 8) would have no real trouble killing me dead in one round of hitting if they rolled just slightly above average.

Yeah a Wizard given time and space is a force to be reckoned with- but if you have neither of those things then you either need to be durable enough to survive being nailed or you need to be hard to find/lock-down to avoid being nailed.

So jumping a bit into Fighter or Rogue seemed like a good bet with my scores. The only reason I wanted 4 in whichever of them was so I could get more Con and thus HP. The more health I have the better my chances of using Necromancy to restore myself should I get hurt. Enervation, Vampiric Touch, or even just managing to kill someone and healing off of that as well.

[Anymage]

If you want heavier armor, a one level dip in fighter won't hurt you too bad. Dipping cleric would be better, but that isn't an option with your stats. (If your table uses UA, artificer might be an option to get some armor while keeping all your spell slots.) But if you want to be able to survive a hit that does connect, casting False Life on yourself before combat and/or asking the cleric to cast Aid at the beginning of the day will likely be more effective than sinking several levels into fighter.

[Bobthewizard]

You're not in wizard for the class abilities. You're there for the spells, especially the high level spells. You are a wizard first and necromancer a distant second.

Wizard 17 gets you wish so don't miss that. Then spell mastery for shield and mirror image might do more for your survival than a few levels of fighter. Then at 19 and 20, you are giving up a 6th and then 7th level spell slot, which are huge boosts in power.

So maybe a level of fighter now for armor would be worth it but there is a significant cost. I wouldn't go more than one level in fighter or rogue. Otherwise, make sure you're utilizing shield, absorb elements, mirror image, misty step, dimension door, contingency, and even the dodge action.

[Dork_Forge]

If you want heavier armor, a one level dip in fighter won't hurt you too bad. Dipping cleric would be better, but that isn't an option with your stats. (If your table uses UA, artificer might be an option to get some armor while keeping all your spell slots.) But if you want to be able to survive a hit that does connect, casting False Life on yourself before combat and/or asking the cleric to cast Aid at the beginning of the day will likely be more effective than sinking several levels into fighter.

Unless it's been errata'd you don't gain heavy armor proficiency from any multiclass, OP would have to get it from a subclass like Cleric (actually I can't think of any other ways besides a feat).

[Degwerks]

Take a few levels of Artificer to get armor and shield and healing.

[ThatoneGuy84]

I wouldnt consider multiclassing wizard at 16.
17 - Level 9 spells to juicy.
18 - Spell mastery is just tooooo good.
19 - ASI (you could take tough feat at this point and get + 2 HP per level back pay for 38 total HP) if you feel to squishy. Ext.
20 capstone I actually dont much love on Wizard, so I'd only multiclass 2 level dip at 18 if I could afford to leave the 19 ASI alone.
But take 19 wiz, dip 1 level cleric if you want better armor prof ect.
Edit nvm u dont have the stats for Cleric.
1 level fighter dip is the option, which if fine if you just want the AC boost of wearing heavy plate.
But by that high level I expect you may no need full plate, depends on your DM and what kind of treasures u have found by then.

[Christew]

My question is how does this work if you've already existing Wizard spell slots from being a level 8-16 Wizard?
Do you gain the three 1st level spells like each class states and then more levels allow you to learn spells as though you're single-classed into them? So possessing no better spell slots to get any higher spells?
OR
Do you gain the three 1st level spells like each class states then more levels allow you to learn spells using your full available multiclassed spell slots? So even though you've only say 4 levels in the not-Wizard subclass you can still pick up say a 3rd or 4th level spell?
OR
Are the three 1st level spells even required to be 1st level or is just assumed you won't have any higher slots available because multiclassing isn't inherently factored into the classes?

You calculate spell slots and spells known separately when multiclassing.

Spell Slots: Pretty straightforward calculations.
Level (Bard, Cleric, Druid, Sorcerer, or Wizard) + 1/2 Level (Artificer rounds up, Ranger and Paladin round down) + 1/3 Level (Eldritch Knight and Arcane Trickster round down) = Caster Level (check against full Caster spell slots table)

Spells Known: A bit more fiddly because classes calculate this differently. You essentially learn spells based on each individual class as though you were single classed and then add the results together.

This is the catch 22 of multiclass spellcasting - you will have spell slots that you do not know spells for.

Example: 8 Wizard / 4 Eldritch Knight
Spell Slots: 8 Wizard + 1/3(4 EK) = 9th level Caster
So at level 8 you would have 4/3/3/2 and at level 12 you would have 4/3/3/3/1

Spells Known: Wizard (6+x Level 1 + 2/level up) knows 20 spells of up to 4th level. Eldritch Knight (4 spells known) knows 4 spells of up to 1st level.

This at level 12, you have 1 5th level spell slot but do not know any 5th level spells. This can be annoying, but is ameliorated by:
1) Upcasting.
2) Spellbook.

Use that higher level spell slot to juice up a lower level spell. If you happen upon a scroll or Spellbook that contains a 5th level spell, write it down.

[SociopathFriend]

Unless it's been errata'd you don't gain heavy armor proficiency from any multiclass, OP would have to get it from a subclass like Cleric (actually I can't think of any other ways besides a feat).

Not to mention we used Point-buy and I went Human mainly so I could have as few odd scores as possible. I'd have to increase my Strength to use most Heavy Armors.
But Fighter only gives Light and Medium Armor when multiclassing.

So at level 8 you would have 4/3/3/2 and at level 12 you would have 4/3/3/3/1

Spells Known: Wizard (6+x Level 1 + 2/level up) knows 20 spells of up to 4th level. Eldritch Knight (4 spells known) knows 4 spells of up to 1st level.

This at level 12, you have 1 5th level spell slot but do not know any 5th level spells. This can be annoying, but is ameliorated by:
1) Upcasting.
2) Spellbook.

Use that higher level spell slot to juice up a lower level spell. If you happen upon a scroll or Spellbook that contains a 5th level spell, write it down.

That is one good part about the mutliclassing idea- as a Wizard I can find spells and gain them entirely separate from leveling up. And I frankly imagine a dungeon made by a mad mage has plenty of those lying around plus there is always the opportunity of buying a spell scroll- though that's an expensive method.

[Chronos]

Note that, even if you do manage to get a high-level spell into your book (it's debatable if that's allowed), you still wouldn't be able to prepare it until you have enough wizard levels. It's still good to hold onto new spells you find (keep the original book if you can't copy it), because you probably will have enough levels eventually, and the standard wizard personality is to accumulate all the spells you can.

[Christew]

RAW I believe you can scribe spells based off of spell slots, not spells known. Writing spells in your Spellbook is gated by spell preparation per PHB.

Copying a Spell into the Book. When you find a wizard spell of 1st level or higher, you can add it to your spellbook if it is of a spell level you can prepare and if you can spare the time to decipher and copy it.

Spell preparation is gated by available spell slots per PHB.

You prepare the list of wizard spells that are available for you to cast. To do so, choose a number of wizard spells from your spellbook equal to your Intelligence modifier + your wizard level (minimum of one spell). The spells must be of a level for which you have spell slots.

By the transitive property, if you can scribe any spell you can prepare and you can prepare any spell for which you have spell slots then you can scribe any spell for which you have slots.

[JNAProductions]

Except that's a class feature, and multiclassing is (technically) a variant rule.

RAW, you can maybe argue that you can scribe a Scroll of Wish as a Wizard 1/Cleric 19, but RAI is certainly not.

[bid]

RAW I believe you can scribe spells based off of spell slots, not spells known. Writing spells in your Spellbook is gated by spell preparation per PHB.

That's a wizard's feature and therefore will only use your wizard level as if your other levels did not exist.

What you are saying is that a cleric 16 / wizard 1 can prepare wish. Nonsense.

[SociopathFriend]

Just to make it clear- I absolutely misread the Wizard spell table when coming up with that, "Change at 16" part.

I thought I'd have level 9 spell slots on that alone and extra spellcasting levels from either subclass would be helpful- not required to get a level 9 spell slot in the first place.

I don't have a great deal of experience with campaigns past lvl 12 or so. And this is the first time I've made a mage that wasn't murdered at lower levels (dam Rogues and Ropers...) I guess now there's no particular need to get more than 1 or 2 levels in either non-wizard class.

So it's basically weighted down to whether I want armor and action surge or stealth and cunning action.

[Bobthewizard]

RAW I believe you can scribe spells based off of spell slots, not spells known. Writing spells in your Spellbook is gated by spell preparation per PHB.

Spell preparation is gated by available spell slots per PHB.


By the transitive property, if you can scribe any spell you can prepare and you can prepare any spell for which you have spell slots then you can scribe any spell for which you have slots.

Except the multi classing rules state "You determine what spells you know and can prepare for each class individually, as if you were a single-classed member of that class."

So you can't use mulitclass spell slots to determine what you can prepare as a wizard. You can only scribe and prepare spells based on your wizard level spell slots.

[Christew]

Touche, totally correct. Upcasting is the only recourse then.