Volo’s Guide to Monsters includes stat blocks for 11 different magic-using specialists: wizards from eight different schools and warlocks of three different patrons. The wizards are all at least level 7; the warlocks, even higher. There are also a level 9 war priest, a level 10 blackguard (antipaladin) and a level 18 archdruid. Every one of these spellcasters has a different repertoire of spells. To come up with individual tactics for each of them would take me the next two weeks.
Rather than tackle each one separately, then, I’m going to share some rules of thumb for developing tactics for a spellcasting NPC.
Begin with ability scores
Most spellcasters will want to keep their distance from the action. I say “most” because I’m all about busting stereotypes—having a beefy, brawny guy also be the best dang transmuter in the duchy is exactly the sort of thing I’d do. But more typically, spellcasters—especially wizards—will have low to average Strength and below-average to above-average Constitution, relying on a higher Dexterity to avoid taking damage and their spells to deal it out. Few of their spells require them to get up-close and personal (that’s more of a cleric/paladin thing), so they’ll prefer to keep their distance. What distance is optimal? Somewhere between 30 feet and the range of their shortest-range spell.
Calculating spell damage
Spell damage depends on two things: number of targets and whether it’s a spell attack or a spell that requires a saving throw. “Expected damage” is the term I use for a calculation of the average amount of damage done times the probability of dealing it. Based on the simplistic premise that the caster’s spell attack modifier and the target’s armor class will cancel each other out (I don’t use this premise myself, but you can use it as a shortcut), the probability of hitting a target with a ranged spell attack is roughly 50–50, so the expected damage is half the average damage on a hit. (For example, scorching ray, cast at 2nd level, deals 2d6 fire damage per ray, or an average of 7 hp. The spell’s expected damage is therefore 3.5 hp per ray.) Since spells that require saving throws usually do half damage on a success and full damage on a failure, multiply their average damage by three-fourths to calculate expected damage.
To calculate the damage of an area-effect spell, use the Targets in Area of Effect table on page 249 of the Dungeon Master’s Guide to figure out how many targets the spell should hit, then multiply the expected damage for one target by that number of targets. Assume that the spellcaster won’t cast that spell unless he or she can catch at least that many targets in its area of effect.
Spell attack modifier and spell save DC are chained together, so you won’t ever get a caster with an unusually high spell attack mod and an unusually low save DC, nor vice versa. Because of this, you’re not going to end up with casters who either specialize in spell attacks or avoid them. You will see an overall preference for save-dependent spells among all casters, simply because such spells usually do some damage even when the targets make their saves, thus increasing these spells’ expected damage by about 50 percent.
Generally speaking, a spellcaster will bring out his or her biggest guns first. But there are exceptions. A particularly cocky spellcaster might prefer to expend as little effort as possible at first, ramping up the damage only when he or she realizes that the opposition aren’t pushovers.
Time’s not on your side
Fifth-edition Dungeons and Dragons assumes that a typical combat encounter lasts three rounds, maybe four or five. Spellcasters often have more spells than time to cast them. Therefore, it’s really important to identify their most efficacious spells before the encounter begins. As of this writing, the EN World forums host a series of useful guides on the various character classes which, among other things, offer assessments of spells color-coded by efficacy (here are links to the wizard, warlock, sorcerer, paladin and bard guides—unfortunately, the cleric and druid guides don’t include spell lists). Any spell in your NPC caster’s list that’s coded red or purple, just cross it off. Any spell that’s cast as a ritual, or that has neither a damaging effect, a defensive effect nor a movement effect (e.g., most divination spells), cross it off.
On the other hand, spells that enhance a character’s action economy are worth their weight in gold. These are the spells that are cast as either a bonus action or a reaction, which means they can be combined with other actions (though leveled spells cast as bonus actions can’t be combined with other leveled spells, only with cantrips). Paladins have a lot of these: compelled duel, divine favor, shield of faith, magic weapon and all the smite spells. Clerics have healing word and mass healing word, sanctuary, shield of faith, spiritual weapon (this one is so good, you have to assume that any NPC who has it casts it before doing literally anything else) and divine word. Druids have healing word, flame blade, grasping vine and the shillelagh cantrip. A bard may have feather fall or healing word. Wizards and sorcerers have expeditious retreat, feather fall, shield, misty step and counterspell, and wizards additionally have magic weapon, which they should cast on their staves or daggers when an enemy gets within melee range of them. Warlocks have expeditious retreat, hellish rebuke, hex, misty step and counterspell.
Any bonus-action spell that’s applicable to the situation, plus a damaging cantrip, is at least as good as a leveled spell that takes an action to cast. Spiritual weapon, I have to mention again, is truly spectacular, because it keeps going without concentration, providing a bonus action every turn, until the combat encounter ends. (Technically, until 1 minute has gone by, but that’s a 10-round combat encounter. Combat never lasts that long.) And wizards and sorcerers should always keep a spell slot in reserve for shield or counterspell.
The value of spell slots
I value spell slots not by their level but by their scarcity. The rationale for this is that a fireball cast using a 4th-level spell slot is as good as any 4th-level spell. However, higher-level spells tend to have effects that lower-level spells don’t duplicate. In other words, if all you want to do is hurt someone with fire, you can use fireball, or you can use scorching ray, or you can even use fire bolt. But if you want to become invisible and stay that way even if you’re attacking or casting spells, you’re going to have to cast greater invisibility.
A level 9 wizard has four 1st-level spell slots; three 2nd-, 3rd- and 4th-level slots; and one 5th-level slot. That wizard will only use his or her 5th-level slot to cast a 5th-level spell, period. Why? Because there’s no other slot he or she can use to cast that spell. It’s unique.
On the other hand, those three 4th-level slots can be used to cast 4th-level spells or 2nd- or 3rd-level spells boosted to 4th level. This is where expected damage calculations come into play, because, for instance, the 3rd-level fireball spell does more damage when boosted to 4th level than the 4th-level ice storm spell does. Ice storm is 4th-level because it produces an additional movement-impeding effect; if you don’t need to impede movement, you may as well just boost fireball for the extra damage. Wizards tend to be smart cookies, and they know what their spells can do. They’re good judges of which spell suits the occasion better.
The wizard won’t waste a 4th-level slot on boosting a 1st-level spell, though. Those are simple, dime-a-dozen utility spells. There’s nothing they can do, even boosted, that a higher-level spell can’t do better. And the wizard’s four 1st-level spell slots aren’t good for anything except casting 1st-level spells. So anytime the wizard needs to cast a 1st-level spell, he or she will use a 1st-level slot for it.
Note that warlock spells are always boosted to the caster’s highest spell level, no matter what. Warlocks also have very few spell slots, so they have to make every spell count.
Each NPC spellcaster archetype has a special feature related to his or her specialty. These I’ll look at individually, because they affect the spellcaster’s tactical decisions in different ways.
- The abjurer has Arcane Ward, a recharging magical barrier that soaks up damage that would otherwise affect him or her. The main effect of this ward is to allow the abjurer not to retreat if charged by a melee attacker. This ward, plus a high Constitution, lets the abjurer survive in the middle of the fray for longer than a spellcaster normally would. Since the Arcane Ward is recharged by the casting of abjuration spells (helpfully marked with asterisks in the stat block), an abjurer who’s under attack by a melee opponent may cast abjuration spells (e.g., mage armor) specifically for the purpose of recharging the ward. However, the spells he or she casts in straightforward self-defense (such as shield and stoneskin) may be enough to accomplish this by themselves.
- The archdruid has Change Shape. One word: mammoth.
- The blackguard has Dreadful Aspect, which affects every enemy within 30 feet. He or she therefore has a strong incentive to wade right into the middle of the fray. Combined with the high-Strength, high-Con ability contour of a brute, this suggests a pure tank style.
- The conjurer has Benign Transportation, allowing him or her to teleport up to 30 feet as a bonus action each time he or she casts a conjuration spell (marked in the stat block with an asterisk). Useful as a way of maintaining distance, but also useful for getting out of trouble by swapping places with a tougher ally.
- The diviner has Portent, which is
a bailout measure that doesn’t affect his or her tactics in any waymuch more useful as a risk reducer than I realized way back when I first wrote this. In particular, see Fuligin’s comment below.
- The enchanter has Instinctive Charm, also a bailout measure.
- The evoker has Sculpt Spells, which lets him or her semi-safely cast damaging area-effect spells with allies inside the area of effect—kind of a big deal, especially since the evoker has a lot of those spells.
- The illusionist has Displacement, which he or she should be using all the time, especially considering that it’s a non-spell bonus action, so it can be combined with a leveled spell in a single turn.
- The necromancer has Grim Harvest, which gives him or her an incentive to rely on necromancy spells (marked in the stat block with asterisks) as much as possible.
- The transmuter has Transmuter’s Stone, which has one of several different effects, and it’s cheating to decide that it starts off with exactly that effect that will be most effective against your player characters. Pick one that suits the transmuter’s stats and personality. That being said, a transmuter with a speed boost stone will use it to Disengage from melee and maintain a safe distance from enemies; the other options won’t affect the transmuter’s tactics. However, since the transmuter can change the effect of the stone on the fly as a free action after casting a transmutation spell, it can make informed decisions once it sees what the PCs are capable of. In a subterranean setting, against a party comprising only humans and halflings, it may make sense to choose the darkvision effect, then take out the lights. Against chargy melee fighters, the speed boost is helpful. Against one or more rogues, the Con save proficiency offers resistance against poison. Against a magic-user casting spells that do elemental damage, or against magic weapons that do the same, resistance to the appropriate element is de rigueur. The transmuter is intelligent enough that he or she can make an educated guess about the PCs’ predilections after one round of combat, without having to actually suffer damage from any of the aforementioned situations.
- The warlock of the Archfey has Misty Escape, a handy bailout measure, but also one that allows him or her to make a subsequent attack from hiding, an opportunity he or she should make the most of.
- The warlock of the Fiend has Dark One’s Own Luck. The time to use this is when the warlock is moderately wounded (reduced to 54 hp or fewer).
- The warlock of the Great Old One has Whispering Aura, a passive effect. Since it has a range of 5 feet and affects everyone the warlock wants it to affect—and since the warlock also has a high Constitution—he or she has every motivation to wade right into the midst of his or her enemies.
When to flee
It takes a lot of work to become a wizard, and that’s not an investment that wizards take lightly. They’re also, usually, fragile flowers. They need only be moderately injured (reduced to 70 percent of their maximum hit points or fewer) for discretion to seem like the better part of valor. They tend not to have great ACs or move unusually quickly, so their best choice is to Dash (action) away without further delay, unless they have some kind of spell or feature that can cover their escape, in which case they’ll use that spell or feature, then Dash on their next turn.
Other spellcasters live closer to the edge (and also tend to be more durable). It takes being seriously injured (reduced to 40 percent of their maximum hit points or fewer) to induce them to run away. A paladin probably won’t run away at all; he or she will bravely fight as a rear guard while his or her allies retreat, and only once they’re safely removed from the battle will he or she Disengage and withdraw.
Next: yuan-ti, revisited.