This part 2 of a probable 4-part series on designing spellcasting features. Part 1 can be found here.

Let's talk about full casters!

These, of course, are character archetypes that get full spellcasting progression. This means their maximum spell level goes up at every odd level-up, and they gain additional spell slots at almost every level-up. A 1st-level bard has 2 slots, but that pace of advancement builds up quickly: they get 9 slots by 5th level, 16 by 11th level, and top out at 22 slots at level 20. I generally balance content assuming games include 12 rounds of combat per day, so for most of the game, I assume a full caster can afford to cast a spell every round.

With all that magical firepower, it should be pretty clear that how you design your spellcasting features is key to how these archetypes function. As with last week, I'll focus mostly on wizards, but I'll touch on some of the other classes towards the bottom.

Stronger Spells

Numbers Go Up

Most obviously, we could give our casting subclass features to straightforwardly empower their spells. If you survey the official wizard subclasses, you will see there are...none of these, not for core features that kick in at level 2. They're pretty rare at higher levels and across other classes, too. Last time, I said that numbers-go-up features tend to pack a lot of power with a relatively small amount of flavor. With a character who can afford to cast spells every round, that power only increases. There are a few, but they tend to be rare or pretty tightly scoped.

More Reliable

In WotC's subclasses, you will see a ton of this style of feature. Sculpt Spells, Portent, Awakened Spellbook, Potent Cantrip, and more. The appeal is obvious: it reduces the number of feels-bad moments where the enemy saves or the spell fizzles or you can't find the right targets or whatever (which, as a full caster, you'll see a lot of). But it doesn't increase the damage ceiling the way a straight numeric boost would.

Keep in mind that reliability is another form of power, in a game that eventually boils down to statistical success chances. A Divination wizard's Portent is incredibly strong without directly increasing any numbers.

More Upcasting

WotC has, to date, only used this pattern twice (and explicitly only used it once). On the Order of Scribes, they attached it with such tight usage restrictions that its power is very limited (1/day, only a 1st- or 2nd-level spell, has to be an action). The Enchantment wizard gets Split Enchantment, which gives an additional target to any enchantment spell that only has one target; in practice that means you're getting a free upcast when you cast a Dominate spell or, at the highest levels, a Power Word. It's fine (and still strong, even) to get extra targets from command or hold person with this, but that requires you to be casting them at base level, so you're still using lower-level slots and keeping your power ceiling in check. It feels good to get that extra target, but you could already do that if you had to just by upcasting as normal.

How I Do It

I've put versions of all these things on wizard subs. But it's fair to be concerned about power. WotC's wizard subs have a strong tendency towards always-on benefits; the easy way to cap this stuff is to attach some usage limits. In fact, when I look at my own wizard subs, every single one with some sort of power boost at level 2 has a usage limit on it.

More Spells

This isn't terrible to put on a full caster but isn't necessarily that fun. They already generally have access to a lot of spells, so giving them more may not make things better. Consider the Divine Soul Sorcerer, which gets access to the entire cleric spell list. I have never seen a player struggle as much as someone trying to pick spells with that gigantic range of possibilities.

Obviously you've got things like a sorcerer's bonus spell list or a warlock's expanded spell list, and those are standard (and sorcerers do love to get a few extra spells known). But full casters already get big spell lists, so it's generally more interesting to give them better ways to use what they already have.

More Spell Slots

Yeah, probably don't do this one for a full caster. They don't need the extra slots.

The exception is if it's core to the theme for your subclass to be casting specific spells. So my Order of Exploration gets to cast Tieleman's cannon for free, because they're a ship's wizard, they absolutely should be summoning cannons.

Spells as Triggers

This is the good stuff. You want your features to incentivize the player to act out the fantasy they're playing. If they're playing a full caster, that probably means casting spells, so it's great to give them features that make them cast spells.

Abjuration wizards get a cool effect when they cast an abjuration spell. Necromancy wizards get a cool effect when they cast a necromancy spell (well, in theory; WotC overlooked the fact that necromancy direct-damage spells mostly suck, and healing can be underwhelming on a wizard who's not often taking much damage).

As an anti-example, consider the Enchantment wizard, which gets Hypnotic Gaze: a 2nd-level feature that takes an action to incapacitate one target. It requires your action every turn to maintain it. While you're Hypnotic Gazing, you're not casting spells, you're not doing damage, you're not even going anywhere (because you have to stay adjacent to the target). It's a strong control effect, but using it requires you to avoid doing the thing wizards are meant to do (casting spells). Indeed, it requires you to avoid doing anything at all. Lame.

So here's the big lesson: write features that encourage behavior that reinforces your fantasy. For full casters, that's casting spells, so give them features that make them want to cast spells.

Casting Time

This is powerful but easy to implement; anytime you give a full caster "cast an action spell as a bonus action", they're going pair it with a cantrip. That's not a reason to avoid it, just know what you're doing. When you write a bonus action spellcasting feature, it's almost always equivalent to writing "When you cast a spell, deal 1d8/2d8/3d8/4d8 bonus damage".

Conditions

Condition interactions aren't ideal on full casters; the glory of having a whole spellbook's worth of toys is flexibility, so it's rare to see a full caster who doubles down on inflicting a single condition. They can work for casters who naturally specialize though, like Enchantment wizards.

Concentration

I mentioned a few concentration boosting feature styles last time; these are almost always most relevant on full casters. Your concentration slot is a key part of your toolkit as a full caster (at high levels, it can be the most important part). So full casters are where you, as a designer, are going to want to put your concentration features. But be careful not to make them too powerful. (Seriously, don't write a straightforward double-concentration feature. It's gonna be too strong.)

Loaner Spells

Loaner spell features are ones that let other creatures cast your spells for you. These are great. They use a full caster's primary resource, they reinforce what the caster wants to be doing, and they require teamwork to use effectively. A+, would write again.

They're not right for every theme, but when they are, the mechanical effects tend to work out really well.

Vancian Spells

As with loaner spells, these features tend to need specific themes to work well. They can be a lot of fun, though, especially if they're still spending your spell slots, just in different ways. At mid-to-high levels, full casters have an excess of slots, so Vancian-style features can be a fun way to use up a few more of them.

What if It's Not a Wizard

I really buried the important part of this post, didn't I? It was up in Spell Triggers — you want to incentivize your player to be doing the thing that makes the fantasy work. So a druid should either get an alternate use for Wild Shape or get features that encourage them to make use of it. A support cleric should get features that benefit buff and healing spells; a front-line cleric should either get direct incentives to be on the front line or buffs to the spells that help them stay there.

For an anti-pattern example, consider a Nature cleric. It can use its Channel Divinity to charm plants and animals, which makes 3/10 of its domain spells mostly redundant. It can reduce some elemental damage, which is fine. And its level 17 feature doubles down on that Channel Divinity. Nothing in the subclass encourages much of a playstyle, nothing encourages any particular fantasy (except being a druid without a metal allergy), and in fact its features and spells anti-synergize. It's not terrible, merely underwhelming. But its domain spells are central to the fantasy it's trying to evoke. So it could probably do with either a different Channel or a different selection of druid spells, and a feature somewhere that has cool interactions when it casts druid spells.

Next Time

Part 3, I suspect, will be a little more brisk; we'll go into half- and third-casters and how these features do or do not work for them.