The mage was complicated; the archmage, even more so. Strap in.
As with the mage, the archmage’s ability scores imply an aversion to melee combat, a strong self-preservation impulse, and a strategically and tactically savvy view of the battlefield. We can also determine, by reading between the lines, that the archmage is a wizard of the abjuration school, because Magic Resistance is a feature that abjuration wizards obtain at level 14. Mechanically, that doesn’t mean much, since Magic Resistance is the only abjuration feature the Monster Manual gives the archmage; still, this inference adds a dash of flavor to our archmage’s personality. Abjuration is the magic of prevention. All other things being equal, the archmage’s primary impulse is to shut you down.
The mage’s spells topped out at 5th level, but the archmage’s go all the way up to 9th, with only one slot each of the top four levels. I assume this was to simplify an already extremely complicated and powerful enemy. What it means for us is that those four slots are reserved exclusively for the archmage’s four highest-level spells: time stop, mind blank, teleport and globe of invulnerability. And mind blank, according to the MM, is pre-cast before combat begins—along with mage armor and stoneskin—so that slot isn’t even available. (How does the archmage know to combat is about to begin? Dude, 20 Intelligence. “Nolwenn an Gwrach, Supra-genius!”)
Funny thing about that stoneskin spell, by the way: It requires concentration. That means that the archmage has to drop it in order to cast globe of invulnerability, scrying, wall of force, banishment or fly. And that means that the archmage can lose his or her resistance to physical damage from nonmagical weapons in the midst of combat. If that’s not an oversight on the part of the writers, it means that the archmage has to consider very carefully whether dropping stoneskin to cast another sustained spell makes sense in any given situation. I’m going to plant my flag and say there’s no situation in which it makes sense to drop stoneskin for scrying, even though that spell allows a caster to shoot a spell around a corner. The archmage’s action economy doesn’t leave room for tactical combinations more elaborate than misty step plus fire bolt.
Speaking of action economy, what about spells cast as reactions? The archmage has only one: counterspell. (No shield!) Everything except this and misty step requires a full action to cast. Therefore, the archmage can’t exploit clever combinations to optimize his or her efficacy. He or she has to cast the right spell at the right time, every time.
So let’s take a look at these spells.
- Time stop is a doozy, allowing the archmage to take 1d4 + 1 turns in a row, uninterrupted—but only if none of those actions affects anyone else! As a way of supercharging the archmage’s damage, it’s a dud, but as a way of giving him or her time to set up various defenses, it has promise. We’ll come back to that. It also has the obvious application of enabling a high-speed getaway, but . . .
- Teleport is even better for that. In fact, since it can only transport willing subjects and/or inanimate objects, escape is the only combat application for this spell.
- Globe of invulnerability blocks any spell of 5th level or below, with the opportunity cost of having to drop stoneskin. This requires the archmage to calculate who’s capable of inflicting greater damage: spellcasters slinging low- to mid-level combat spells or ranged and melee foes wielding nonmagical weapons. And the archmage can’t really make this calculation until he or she sees what the player characters can dish out. A sound conclusion is that the archmage makes the switch as soon as he or she is dealt more damage over the course of a single round by low- to mid-level spells than by nonmagical weapon hits—which means you as the dungeon master need to keep track of both, separately.
- Cone of cold is a good way to whack around half a dozen enemies with 8d8 cold damage in a single shot. The archmage has to cast this one early, because of the shape of the spell’s area of effect: as we saw when analyzing the beholder, it’s easier to catch a whole bunch of enemies in a roughly 60-degree arc when they’re far from you and generally all in the same direction than when they’re surrounding you up close. This spell is boostable, but the archmage doesn’t have higher-level spell slots available to boost it with.
- Scrying is a nothingburger during combat. Ignore it.
- Wall of force is a marvelous way to keep an entire party of PCs at bay. It’s also a continuous spell, which means it requires the archmage to drop stoneskin. It repels all physical objects, including missiles, but it’s invisible, so it doesn’t stop PCs from casting spells through it. A logical reason to cast this spell is if the archmage is taking more damage from magical missile weapons than from spell and melee attacks combined. It may be useful cast as a defensive measure, before any of the PCs is able to get within 10 feet of the archmage. But just as wall of force and stoneskin can’t be sustained at the same time, neither can wall of force and globe of invulnerability. The archmage has to choose.
[As McGyrk comments below, a tweet by Mike Mearls implies, though it doesn’t state explicitly, that wall of force blocks spells as well. The rule as written doesn’t support this—it only says, “Nothing can physically pass through the wall” (emphasis mine)—and there’s no erratum for this spell. Unless and until someone at Wizards of the Coast explicitly states otherwise, I stand by my interpretation.]
[Mike Mearls has now confirmed my interpretation. Thanks, Mike!]
- Banishment targets, at most, two opponents (since the archmage’s 6th- through 9th-level spell slots are off limits), and it’s also continuous. The time to use this spell is when one or two opponents are doing more damage than all other opponents combined.
- Fire shield is a pleasantly uncomplicated defensive spell that doesn’t have to be sustained and does some freebie damage to melee attackers. Unfortunately, the archmage doesn’t know whether to use it to resist fire damage and deal cold damage or vice versa until an enemy casts a spell that does one of these, so it’s not a spell the archmage necessarily wants to cast right away.
- Counterspell is a no-brainer, and the archmage should feel free to cast it at up to 5th level (if only once) to keep incoming damage at bay long enough to choose the best defensive measure.
- Fly is a useful getaway spell . . . if you don’t have teleport. If you have teleport, why would you bother with fly? Being a sustained spell, it requires the archmage to drop whatever other defensive spell he or she is sustaining. It looks cool, but considering its opportunity cost, I can’t see what tactical application it might have.
- Lightning bolt—what more need be said? Zots enemies for 8d6 lightning damage apiece; position yourself right, or catch ’em while they’re clustered, and you can nail several PCs with it at once. Casting it at 4th or 5th level is probably too greedy, since those slots may be required for fire shield, cone of cold, wall of force or a clutch counterspell.
- Detect thoughts . . . why? Useful for social interaction only, and super-rude.
- Mirror image is a no-brainer, buying time against attacks from all non-spellcasters. I can’t think of a reason why this wouldn’t be the first spell the archmage casts.
- Misty step is good for tactical repositioning and, because it’s a bonus action, can be paired with the fire bolt cantrip (or shocking grasp, but generally speaking, the archmage should be repositioning away from his or her enemies, not right up on them).
- Detect magic . . . [shakes head sadly]
- Identify—the only identifying the archmage needs to be doing right now is which PC to take out first.
- Magic missile—at level 18, for an archmage to be casting magic missile is like an electrical engineer building devices out of a Radio Shack 150-in-1 Electronic Project Kit. The highest level to which the archmage can boost a magic missile spell is 5th, hurling seven 1d4 + 1 force darts. It’s time to grow up and put away childish things.
- Fire bolt, when cast by a level 18 wizard, does 4d10 fire damage, equaling or surpassing magic missile without costing a single spell slot.
- Shocking grasp, similarly, does 4d8 lightning damage for the archmage, and the recipient of the jolt is deprived of his or her reaction for a round. It also requires the archmage to be next to the target, however, and that’s not where the archmage wants to be, in all likelihood.
Finally, although the MM doesn’t spell it out so explicitly, the archmage has Spell Mastery over disguise self and invisibility. This means the archmage can cast them without having to expend a spell slot; however, the archmage does still have to expend time, in the form of one turn’s action.
As we can see, so many of the archmage’s choices depend wholly on what the PCs choose to do that in the first round of combat, he or she has only one unambiguously sensible choice, and that’s mirror image. Additionally, the archmage will use counterspell to squelch one incoming damaging spell. (He or she won’t waste counterspell on negating a spell that a PCs is using to buff the party.)
Once the archmage has had a chance to see what all the PCs can do, it’s time for a reassessment of defensive measures. Is the majority of damage coming from spells of 5th level or lower? Then the archmage should switch from stoneskin to globe of invulnerability. From missile fire? Wall of force. From one or two specific PCs who aren’t obviously bards, paladins or sorcerers? Banishment.
For a fast switch-up combo, the archmage casts time stop. This gives the archmage a minimum of two extra turns. One will be used to switch from stoneskin to a different defensive spell requiring concentration, if need be. One—always the last one available—will be used to cast either cone of cold or lightning bolt. The archmage’s next priority, if the PCs dealt or tried to deal fire or cold damage, is to cast fire shield to resist that type of damage (if the PCs dealt or tried to deal both types of damage, the archmage will resist whichever type accounted for the greater portion). Any action(s) left over will be used to move to the best location on the battlefield, which will most likely be away from the melee fighters and behind the party’s back line.
If there’s no need to switch away from stoneskin or to cast fire shield, the archmage won’t bother with time stop right now. He or she will simply cast cone of cold or lightning bolt instead—or misty step plus fire bolt if there’s an urgent need to be somewhere else, such as if the archmage is surrounded by melee foes and his or her mirror image doubles are already dispelled. (Invisibility works just as well if the archmage doesn’t need to move farther than his or her maximum movement speed, and it doesn’t cost a spell slot. But invisibility takes a full action and therefore can’t be combined with fire bolt. All it does is buy time.)
There will quickly come a point at which the archmage is out of slots that can be used to cast damaging spells. (If the archmage has determined that globe of invulnerability will be neither necessary nor useful in this combat scenario, the 6th-level spell slot can be considered available for a lower-level spell.) If victory doesn’t seem close at hand, and if the archmage doesn’t have some pressing reason to keep fighting—such as defending a location or item, or because he or she simply hates the PCs’ guts—he or she will teleport out of there. The same goes if the archmage has taken moderate or greater damage (reduced to 69 hp or fewer). If the archmage is seriously wounded (reduced to 39 hp or fewer), he or she will abandon ship even with a good reason to keep fighting.
Surrendering generally isn’t something even most good- or lawful-aligned archmages will be inclined to do: they’re withdrawn by nature, rather than aggressive or compliant, and many of them are suspicious of anyone who might hold power over them. Because of this tendency to distrust others, they’d rather make a clean getaway than plead for mercy. Stuffing the archmage’s teleport spell with a counterspell may change his or her mind about that—or may cause him or her to freak out and fight to the death instead.
If the archmage does calculate that he or she can achieve victory despite being out of 3rd- through 6th-level spell slots, he or she will continue to fight using fire bolt, shocking grasp and/or magic missile to finish the PCs off.
Next: How fifth-edition Dungeons and Dragons gets tribal warriors all wrong.