This is part 4 of 4-part series on designing spellcasting features. You can find Part 1 here, Part 2 here, and Part 3 here.

It's Gish day, baby!

For the unacquainted, "gish" is the general term for any sort of fighter/mage, spellsword-style character: someone who blends magic and martial attacks together. The term originated in early-edition D&D with the Githyanki Gish, an NPC type that was explicitly a fighter/mage hybrid, and has since become the general word for any sort of spellsword build. Part-casters aren't automatically gishes, though: what you want is some mechanic that incentivizes them to actually interweave their spells and their attacks (preferably in melee). In 5E, gishes can come from either direction: full-casters with martial abilities or part-casters who use their spells as part of their ordinary combat rotation. Gishes are usually arcane casters, and their spells are usually direct-damage, but those aren't hard rules.

The best-known gishes are the official ones: the Eldritch Knight fighter and the Bladesinger Wizard. Arcane Trickster rogues might be honorary gishes: when 5E came out they would rarely use spells in combat, but at tables including the SCAGtrips (Green-Flame Blade and Booming Blade), Arcane Tricksters usually use those as their basic attacks. For third-party gishes, there are dozens of dedicated magus classes out there: my favorite is KibblesTasty's Spellblade.

Featurewise, as you might expect, there's a big difference between half-caster and full-caster gishes. The last three posts I've organized by feature type, but for this post, we'll come at it from the archetypes.

War Magic: What is it Good For?

War Magic is the Eldritch Knight's 7th level feature.

Beginning at 7th level, when you use your action to cast a cantrip, you can make one weapon attack as a bonus action.

Bladesingers received ordinary Extra Attack in SCAG but a giant buff in Tasha's.

Sword Coast Adventurer's Guide: Starting at 6th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.

Tasha's: Starting at 6th level, you can attack twice, instead of once, whenever you take the Attack action on your turn. Moreover, you can cast one of your cantrips in place of one of those attacks.

(In D&D 2024E/5.5E, Eldritch Knights get the same buff).

This is by far the most obvious way to create a gish: you have a character who can seamlessly swap a cantrip into their attack rotation. While War Magic vs. Bladesinger Extra Attack seem pretty similar, that bonus action is very important. A 2014 Eldritch Knight can start attack+cantripping at level 7; with Firebolt, they'll actually be dealing the same damage as if they were just attacking (they can squeeze out a bit more damage with Poison Spray). But with that bonus action free, they can squeeze in another attack (via two-weapon fighting or Polearm Master), they can bash with Shield Master, or they can cast a leveled spell with a bonus-action cast time. The other big lever that applies is the SCAGtrips: Green-Flame Blade and Booming Blade both let you make a weapon attack as part of the spell. While they're balanced enough against other cantrips in a vacuum, they're a lot more trouble on a character that's naturally built for melee. I won't belabor the math here, but Booming blade gives an EK about a 50% damage boost.

Should you War Magic?

I'm not gonna say "never". In particular, if you're creating for 2024E, WotC has just decided that "replace one attack with a cantrip" is the standard design pattern, and if it's overpowered, that's the GM's problem. What I'll say is that the 2014-version, "1 attack + bonus action", is way easier to handle for balance math than the open-ended "replace 1 attack with a cantrip".

For an example that uses this pattern well, you can look at Kibbles' Spellblade. It only ever gets one attack — no Extra Attack here. (Which I love; it feels much more like a rogue than a fighter, as a result). After level 5, it gets a feature that is effectively "1 attack + cantrip as a bonus action", and this puts its damage right on pace for tier 2. A huge number of magus/spellblade classes push for Extra Attack at 5 with "replace 1 attack with a cantrip", and they almost all wind up dealing way too much damage as a result.

Part vs. Full

There's a big difference (duh) in how part-caster gishes work vs. full-caster ones, and designers who get that difference wrong can cause a lot of damage. Part-casters need buffs to their spell output, to make sure they don't underperform when relying on their spells. Full-casters need scare-quotes "nerfs" to it. Not that you're actually going to nerf their casting: nobody would pick a subclass that nerfed their core feature. But a full-caster gish needs something to prevent them from acting like a full caster.

The Bladesinger is our primary illustration of this problem. In tier 1 and tier 2, its Bladesong feature can give it goofy-good AC, and it can function as a very effective martial (that also happens to cast spells). As you get to higher-level play, though, its AC gets less remarkable, its low hit points become a bigger weakness, and, more importantly, its spells get better. So functioning as a martial starts to be suboptimal play; its spell power outstrips its martial ability. High-level bladesingers, accordingly, tend to stand back and just function as high-AC wizards. The Bladesinger is a failure as far as gish design goes.

On the flip side, the Eldritch Knight can also be described fairly as a failure of gish design. If you're optimizing for damage and not using the SCAGtrips, it winds up with a distinct (and unintuitive) attack pattern: weapon attacks for levels 1-6, attack + cantrip for levels 7-10, and then back to just doing weapon attacks for level 11+. (If you are using the SCAGtrips, then it's attack + Booming Blade at level 7 and never look back.) And the EK's leveled spells are never really a big component of their damage: because their spellcasting DC is likely to lag behind so much, they tend not to cast damage spells. Among optimizers, the EK's go-to playstyle is to spend all their spell slots on shield, and just be a giant tank thwacking out Booming Blades. The EK feels a little gishier during the stretch where War Magic is important, but ultimately doesn't carry the fantasy well.

Features for Part-Caster Gishes

The good news here is that you have a lot of options for part-caster gishes. The only really big pitfall you need to avoid is that you don't want them to come out as better casters than a dedicated caster (see part 3).

Stronger Spells: Generally fair game, but be careful not to outshine the full casters.

More Spells: Most half-casters get bonus spell lists at this point in 5E design. Again, don't outshine your full casters. Single-classed wizards should still dominate when it comes to quantity of spells known.

More Spell Slots: This can work well for a gish, especially if you're got other features that successfully get them casting spells all the time.

Spells as Triggers: Surprising nobody, I really like these features. My Knight-Invoker gets a damage boost to its attack after it casts a spell; this makes it a good idea to interweave casts and attacks (and you can math it actually like a stronger-spells feature). My Knight-Abjurer is more defensively-focused, but gets a similar feature at level 7.

Casting Time: I spent a lot of words up above on "attack + bonus action cantrip" and "replace one attack with a cantrip". My opinion is that BA spellcasts are good features for part-caster gishes when used with limits. So make it limited uses, or leveled spells only, or something like that. Make sure to do your damage math so things stay within limits.

Conditions: I wouldn't usually lean into condition features for a gish. There are exceptions; I can imagine a poison-themed spellblade sub or something. But usually the big idea you've got going on is gishing, so there's not a lot of room left for another.

Concentration: I mentioned last time that concentration boosts aren't ideal on part-casters, because their concentration slot is less important. This should be more true for a gish (but isn't always). Generally, a gish's spells tend to be more direct-damage rather than concentration, so concentration buffs shouldn't be as useful. Plenty of counterexamples exist, though.

Loaner Spells and Vancian Spells: No change from what I said in part 3 here; half-caster gishes dislike and like (respectively) these sorts of features the same as any other part-casters.

Features for Full-Caster Gishes

As referenced above, for a full-caster gish, you generally don't want to make them a more effective spellcaster. That's hard. You have to come up with a feature that is cool, and powerful, and fun to play, but also that helps the archetype play against the full casting that comes naturally.

Stronger Spells: Probably don't do this.

More Spells: At a minimum, you'll want to skew a bonus spell list towards stuff that helps with melee combat.

More Spell Slots: Again, probably don't do this. Maybe you can find a way to tie it into the gishing loop, though.

Spells as Triggers: By far your most important tool. This is where you'll come up with a feature that turns spellcasts into a resource for gishing. Maybe casting a spell buffs a melee attack; maybe it buffs AC or grants temporary hit points. But there's a lot to work with for this style of feature.

Casting Time: BA spellcasts and BA attacks are still tempting here. But make sure you're not creating something too powerful. For instance, my Empire Domain gets a limited number of BA casts per day. After that, they have to "downcast" spells to do it—the spell's level gets downgraded when cast as a BA.

Conditions: Same as above, a gish usually won't have thematic or power budget available for condition-oriented features. Never say never, though.

Concentration: On the one hand, if your full caster is wading into melee, they'll probably really want concentration boosters. On the other hand, this can result in them leaning away from a gishing playstyle, if they're instead focusing their attention on high-level concentration spells.

Loaner Spells and Vancian Spells: I don't think I've seen a full gish that uses these too much, but that just means someone should go write it. They're great tools for acting as spell slot sinks, and that can be the right think to get a full caster behaving less like a full caster.

Casting Stat for Attacks: I low-key hate this, but also, it's kind of necessary. Ever since the Hexblade established the principle, it's become pretty standard to allow various gish archetypes to use their casting stat in place of Strength for attack and damage. The issue is that it's a huge chunk of power (huge!), but also not all that exciting. Still, you'll probably want to at least think about it. You'll need to provide some way to use weapons at baseline effectiveness, either here or through some other means.

Out-there stuff: I've written all four of these posts like the menu above are 100% of the features that are relevant. And that's wrong! For one, there are always more options, and more creative options. For two, especially when you're talking about a full-caster gish, you'll want to look at other sorts of features that can force them into melee combat or act as spell-slot sinks. My Ironheart sorcerer gets to conjure weapons and use them to make melee spell attacks. KibblesTasty and Griffon's Saddlebag have both written druid subclasses that get boosts to shillelagh. If you want to avoid the Bladesinger's mistake (it's just a tanky full-caster), you'll probably need to come up with something unique to get a satisfying gish loop.

In Summary

Dammit, don't make me write one of these. I'm tired enough already. Go write a spellcaster! And tell me about it, especially if it's awesome. And especially if something I said is wrong.