Celestial Warlock Tiefling spell and invocations help?

[Nikushimi]

Hey! I have a Tiefling celestial warlock who is the bloodline of Levistus.

My questions are simple. Cold and Radiant themed.

Levistus gives me Armor if Agathys, but only once at level 3 and it is only cast as a level 2 version.

I’m currently level 2 and just got another spell and access to invocations.

I had taken Armor of Agathys and Guiding Bolt as my spells are 1st level, but remembered that I gain the Armor of Agathys because of Levistus.

So is it worth it to still have Armor of Agathys as an actual spell or switch it out for something else? I would switch it out for Arms if Hadar for an area of effect.

The campaign is a 2 person game and the dm. So a total of 3 players. It’s just a small side game based roughly on Tomb of Anahilation.

My other question is what Invocations would be good for my theme? I took Agonizing Blast cause it seems most useful.

I will be Taking Pact of the Tomb and Aspect of the Moon eventually but not sure what else to take for my theme. Eyes of the Rune Keeper seems good but I’m not sure.

Any help would be appreciated! Thanks!

[JackPhoenix]

Tomb of Levistus comes to mind

[Nikushimi]

Tomb of Levistus comes to mind

For the later levels but I’m currently level 2 and trying to decide on things for now.

But Tomb of Levistus is on the list for later.

But focused on the current levels.

[Theaitetos]

Well, obviously you have to take Book of Ancient Secrets, giving you access to all rituals in the game. I recommend Find Familiar as one of your first rituals: familiars are just plain awesome – and a (snow) owl would be fitting your cold theme.

Invocations:

Armor of Shadows (Mage Armor) is very useful unless you have armor proficiencies from multiclassing or something.
Fiendish Vigor (False Life) is strong at early levels but loses its usefulness very fast.
Mask of Many Faces (Disguise Self) and Misty Visions (Silent Image) are strong invocations and very useful if you want to do sneaky things for your small party (rather: duo).
Eyes of the Runekeeper is usually not very useful: You can learn languages in your downtime, so you don't need it to translate things, and then the only use of the invocation is to read hidden or coded messages (although just how much depends on your DM) like Thieves' Cant, Druidic, or magical glyphs.
Devil's Sight is good, but unless you employ or fear the Darkness spell not necessary for a Tiefling (I'd take it for things like a campaign against Drow in the Underdark).
Eldritch Sight is very useful, but once you can cast rituals with your Tome, you can use Detect Magic that way.
Later Repelling Blast is the usual way of making Eldritch Blast even better, but you might want to take the weaker Lance of Lethargy for theme-purposes instead.

Depending on how many battles & encounters you have to overcome, I'd take:
heavy battle: Fiendish Vigor and Armor of Shadows at level 2. At level 3 I'd replace one of them (most likely Fiendish Vigor) with Book of Ancient Secrets.
few battles or no melee threat: Misty Visions and Book of Ancient Secrets.

As for cantrips:

Levistus Tiefling doesn't really work that well with Warlock in this regard, as Ray of Frost is completely useless compared to Eldritch Blast (less damage, worse damage type, both ranged spell attacks), but maybe you can ask your DM to take Frostbite (CON save) instead of Ray of Frost. Otherwise you're well equipped for combat already with Eldritch Blast & Sacred Flame (DEX save, free Celestial cantrip). You also have Light.
That leaves you 1 other cantrip to choose, and at level 3 you can choose 3 more! I recommend Guidance, Spare the Dying, and Shape Water as your Tome-cantrips. Your warlock cantrips: Prestidigitation, Chill Touch and Minor Illusion (if you don't have the Misty Visions invocation).
You might forego Spare the Dying if you trust your Healing Light power to be sufficient, so you can take another cantrip from another class.

[Nikushimi]

First, thank you for those suggestions and thoughts! I want to give a bit more detail on my character to maybe help, and a bit more detail on my problem I'm having in deciding.

Well, currently my Celestial Warlock, Levistus Tiefling looks a little like this.

AC: 14 (leather armor)
HP: 19

Cantrips
Ray of Frost (Levistus Bonus Cantrip)
Light (Celestial Bonus Cantrip)
Sacred Flame (Celestial Bonus Cantrip)
Eldritch Blast (Chosen Warlock Cantrip)
Frostbite (Chosen Warlock Cantrip)

Spells: 1st level, 2 slots, 3 known
Guiding Bolt
Armor of Agathys (Might switch this out for Arms of Hadar)
Cure Wounds (Might switch this out as well, unsure)

Invocations: 2
Agonizing Blast
N/A

So this is my current setup because I can't exactly decide on a 2nd Invocation and since Levistus gives me Armor of Agathys I'm unsure if I should keep Armor of Agathys as an actual spell that gets better as my slots improve or if I should just keep the once a day Armor of Agathys I get from Levistus at level 3 which stays at a constant 2nd level version.

I mainly have Ray of Frost for the reduced speed factor. While I can get it with Lance of Lethargy as well my planned Invocations take up the next few that I gain so it wouldn't be until later that I'd actually take Lance, if at all. Our campaign is a bit more story driven, and what fights there are is usually scaled to what we can handle. So I'm not too worried about maximizing damage. Rather, I'm rather trying to figure out what works thematically and practically.

So at the moment I am trying to figure out
1. Should I replace Armor of Agathys as a spell because I get it from Levistus, but only once a day at a level 2 spell.
2. What Invocations to take to be thematic and practical.

Some more information.

I don't see my guy being exactly sneaky. His background is Hermit. He basically lived in a forest at the base of some cold mountains because he was rather unwelcome where he was born cause of his appearance which is extremely cold and icy. Icy blue frost like skin, snow white hair tinged with light blue, white silver eyes that are extremely piercing (he has an intimidation at level 2 of +7), and just an icy air around him (it's a bit chilly near him).

So he was a bit of an oddity even among other Tieflings. In his seclusion is when he became a warlock. He is rather silent. Preferring to be by himself. He enjoys studying and learning, and he actually wishes to help the world with his gifts. A way to show them "I'm not bad." kind of thing. Extremely socially awkward. Mainly cause of his seclusion and lack of interaction with people aside from the occasional visit to a nearby village for supplies he didn't have in the forest.

So sneaky isn't his way necessarily.

For the future I plan on taking Pact of the Tome for his Pact to get more magic.

Invocations I have planned currently are

Aspect of the Moon and Tomb of Levistus.

The main problem I'm having is once I hit level 3 (when I can actually take Aspect of the Moon cause I will have gotten my Tome Pact) I will be replacing the second Invocation I got at level 2 for Aspect of the Moon. Tomb of Levistus I can't take till level 5.

So I'm basically looking for a placeholder for the 2nd invocation till level 3, but I don't want it to just be anything. Perhaps I just don't take a 2nd invocation UNTIL level 3?

I know, I'm a bit weird.

Sorry for the long explanation and hope this helps to help me. Maybe I'm just being a bit too picky or making it harder on myself.

Thanks for reading this long mess of a comment and hope to hear from more on some thoughts and suggestions!

EDIT: And yes, I will be taking Book of Ancient Secrets. I just don't know when or at what level.