Battlefield Magic - What spells are best and how would you use them?

[CheddarChampion]

The campaign I'm in is shaping up to have us lead an army against a larger, more experienced army.
How can we use magic to prevent this from being a fair fight?

Mostly a thread to share ideas.
Heroism (UA) Paladin 13
Beastmaster 13
Fighter 1/Divine Soul 12
Kensei 10/Horizon Walker 3
(a new character that hasn't been introduced yet) 13
Myself a Conquest 8/Zealot 3/Bard 2

Wall of Fire and Wall of Force seem good to prevent movement
Fireball et al. can quickly take out a small group that manages to push through.
Circle of Death can hit a lot of soldiers at once.
Glyph of Warding if you have the money.
Shatter to destroy stuff like trebuchets.
Move Earth to destroy defensive structures.
Globe of Invulnerability for immunity to low level mages when holding a chokepoint.
Reverse Gravity for a combination of damage and area denial.
Whirlwind for surgical blasting.
Earthquake to destroy a fortress easily.
Meteor Swarm if you're really not interested in the affairs of mortals.

A lot of these we personally can't use, of course. What else can we do?

[Democratus]

How big are the armies? If each army is tens of thousands, then 5 people using battle magic might not have a big effect on the battlefield.

Typical approach is to have the party play the role of "special forces" and go take out some key asset behind the lines, like the leader or an uber-weapon or something.

[airless_wing]

Shame you don't have a Druid in the party; they really are the masters of battlefield control, and can do some wild things at high levels.
Hallucinatory Terrain And Mirage Arcane are absolutely bonkers with large scale, army-style combats. Having the enemy march themselves into a quagmire or canyon are obvious ways to give yourself an advantage.

Your Sorcerer could do some damage with illusions such a Seeming; making an entire battalion suddenly be donning your colors can cause chaos and potential infighting. Wall of Stone can be made permanent, and works great to fortify positions and funnel enemies into compromising spots.

Basic crowd control such as Hypnotic pattern, Faerie Fire, Spirit Guardians are always good.

[N810]

Spiked growth is great for weakening and bogging down a section of the army.

[da newt]

Mold Earth - create home field advantage through extensive trenching / cover.
Any obscurant can make battlefield maneuvers and ranged attacks very difficult.
Illusions - provide targets that aren't real, change colors so you can pass as the opposite troops.

Take out the leadership, cripple their communication / coordination, spread them thin, suck them into ambushes, find the better ground, cripple their supply chain, poison their water, stock up on necromancers so your numbers never actually go down and you can use their casualties against them, create superior range, never let them rest, ...

The smaller force should probably look at guerrilla style warfare and info ops as opposed to direct combat.

Large scale tactics are a whole different beast. Do some research.

[Guy Lombard-O]

Plant Growth is a nice non-concentration fire and forget.

Depending upon what you're facing, Sleet Storm can have great value. Especially for temporarily incapacitating a decent-sized area of enemy archers, or a group of spell casters trying to maintain concentration spells. Great for cutting off support to a section of the battlefield during a counterattack.

[Eldariel]

8th level spells are great for hitting armies. Sadly you don't have access to stuff like Earthquake and Control Weather yet; those are the obvious ones (Control Weather more so as it actually has a big area of effect, but convenient cave-ins and such can also be nice). Control Winds does something too, but its radius is just too small to be of much use on more than a tactical scale, especially as the individual effects are quite weak.

Some good tactical scale effects include Summon Greater Demon, which can get some rather interesting things: summoning a simple Babau and having it spam fear amidst the army as long as it lasts can be quite efficient as the spell is at will and is really hard for mundane creatures to kill, especially if it's amidst soldiers in cover from any focused volleys. A couple of fears can easily do brutal things to formations. Of course, it has the issue that it will run free and disappear somewhat soon unless you can get like DC22 save, where it can't succeed anymore (Robe of the Archmagi + Pale Green Prism Ioun Stone + Casting Stat Tome and 20 base Stat would put you at 6+6+2 = DC 22 on this level). In that case, Planar Binding something like that can actually be worthwhile; it's just a single creature amidst hundreds but a single creature that can break entire offensives can be quite worthwhile. Alternatively, something like Dybbyk could probably wreak even more havoc taking over bodies of the fallen. It would be slower but it would be quite scary.

Useful creatures other than Demons include Elementals (Earth Elemental can really wreak havoc again especially psychologically because OH MY GOD THE EARTH IS SWALLOWING US) and some Devils (but sadly Devils kinda suck in this edition, at least when deployed directly against the opposition - well, unless you can get a Pit Fiend anyways). Conjure Celestial and Fey can obviously also produce some really useful additional casters for your side. To that end, Simulacrum is obviously great as ever.

An alternative to real things, large-scale illusionary creatures like dragons or whatever can also be huge in this regard. Major Image, Programmed Image, etc. have no limit on how many you can have in effect. Fear can be more powerful than actually killing people in war; break a unit's morale and they'll break and enable your allies to strike through on that flank (of course, you have to somehow make it clear to your allies that the Dragon or whatever is on their side - really depends on the army).

Though for killing people, Symbol of Death is probably just the best. Produce as many of them as you can before the fight, deploy them however you see fit in the enemy ranks (glyphed table bombardment, anyone? Though if enemy is advancing, this is unnecessary as well; you can just use the ground) and watch as those 60' radius areas slaughter hundreds and then become impassable areas for the enemy for 10 minutes.


Usually though, the thing PCs do best is target the enemy chain of command. Remove the enemy leaders or their means of communication and the army falls into disarray, friendly forces suddenly attacking friendly forces that they thought were enemies and the like. Simple deception magic is highly effective to this end; even better than dead commander is a dominated commander as long as nobody is aware of that happening. Just try and make it look natural. Of course, it can be complemented with the grand scheme deception magic such as Mirage Arcana as mentioned. To this end, decoding enemy means of communication is absolute key; if they use magical communication, e.g. Sendings or Messages impersonating their commanders can have a huge impact without even going anywhere.

Similarly, enhancing ally chain of command via. telepathic messages, or skywriting or whatever can be a huge player contribution. It's not fancy or obvious but the efficiency of command is basically why modern armies are just so versatile compared to those of the past; in history, getting a message to a group leader could take minutes, which in the heat of combat can be a lifetime and units can easily be lost in that time. This is doubly problematic because the forces on the ground don't have an idea of the overall situation so them taking initiative can jeopardize the entire combat. There are examples of this throughout the history of warfare even from modern times but especially from the past.


Mold Earth is probably the single most powerful cantrip in this kind of scenario as mentioned. Build trenches, walls, etc. in a matter of minutes or hours. Alone.

[CBAnaesthesia]

Lots of good advice already, but also:

If you have opportunity to set up an ambush in a narrow valley or something, Symbol could be a big help.

Storm Sphere would be good for breaking formations and hindering any enemy flying units.

Fabricate for quick prep to make fortifications and such.

[DrKerosene]

Enough people able to ritual cast Leomund's Tiny Hut should be able to do a turtle crawl across a battlefield (if you assume the domes are indestructible vs most methods).

I suppose it could also work for field hospitals, if you say there is no floor so you could pull in unconscious people to get some Prayer Of Healing, or Healing Spirit, or Healer feat, type loving. Also the spell Catnap would be useful with a “safe space” like Tiny Hut should provide. Assuming you don’t exceed the capacity limit.

It would also be an amazing addition to any siege weapon that you can set up. Get yourself a Ballista on a wagon, cast Tiny Hut on the Wagon (if you rule the spell anchors to a surface, like a ship), pull it with a Phantom Steed (takes a minute to fully end). Now you’ve got a suicide squad.

And if you do go with the no floor interpretation, you can conjure medium sized creatures to go outside the dome via whatever tunnel/trench you would have for injured, so you could send out familiars or conjured fiends/fey from relative safety.



A number of Unseen Servants can move multiple things simultaneously, so send them out front to put down those boards to cross the quagmire instead of living things. Use them as shields (give them shields too), make them push mantlets, or hold up sheets to provide obscurement/concealment. Perhaps they can help with the reloading of a siege weapon too.



I think any Druid who can cast Call Lightning and fly around would be a high level asset worth stacking buffs on. Though sorcerers with Extend Metamagic would probably be a little better (if you can just cast fly for a 20+ minutes duration). Extended Tiny Hut would be good too.



If you can prepare the battlefield with some Glyph Of Warding spells, well that seems like we’d need clearly limits on spells available, funds, army sizes, etc.



I suppose the spell Animal Messenger would be relevant, and at least worth considering instead of Sending if spell slots are precious.