Cinco: Group Spellcasting

Sorry to keep Cinco!-posting, but Alex from To Distant Lands wrote a really fun addition to magic which I wanted to share and also slightly refactor:

Metamagic

When you work with another mage(s) to combine your powers into a new spell using the same motif, each of you pay one inspiration. All additional inspiration spent afterward is multiplied by the number of casters for the purpose of defining the effects of the spell.

This is really cool and, I can imagine, produces the cool sort of scene where you get a crowd of mages casting a spell together. My first thought reading it was, oh geez, one of us needs to come up with ways to spend more inspiration (or at least scale up the rules that currently exist)! But that made me think: oh, maybe the approach is backward, and rather than multiplying effects we can treat it as a discount on combined effects. This is my revision:

Multiple mages in one zone with complementary motifs may cast a spell cooperatively. Each ‘helper’ spends 1 inspiration, and the mega-spell’s base damage equals how many mages are cooperating. Further enhancements by spending extra inspiration or using a large arcana are applied to the resulting mega-spell. The mage with the lowest relevant ability attempts the D20 check. This costs 2 actions for everyone, but those with regular sized arcanas give the main caster an extra reroll.

I also rewrote the damage enhancement to deal 2x damage on a hit and 1x on a miss, so it’s clear how mega-spells are impacted. Assuming that’s the enchantment selected, two mages can deal 4 damage on a hit or 2 damage on a miss; three mages can deal 6 damage on a hit or 3 damage on a miss; and so on. The math also comes out kinda the same as in Alex’s original rendition: rather than the effects of spending 1 inspiration being multiplied, though, it’s more like mages casting spells at a discount. On the below table, e equals the number of enchantments, and the right two columns indicate the amount of inspiration that would be spent for the equivalent effect.

Mages	Separate	Cooperative
2	2 × e	1 + e
3	3 × e	2 + e
4	4 × e	3 + e
n	n × e	n + e – 1

For example, three mages can spend a total of 6 inspiration amongst themselves to cast a twice-enhanced spell separately, or they can spend 4 inspiration amongst themselves to cast a spell with the same (or similar effect) cooperatively. Note that there's only ever a discount when a spell is enhanced more than once (meaning e > 1); this means you want to use this to do really crazy shit or, I guess, fluff up minor spells in fiction. Also note that having no enhancements on an arcana is the same as using it as a regular weapon; think of it as a cantrip.

I also thought it’d be fun to broaden applicable motifs from being necessarily the same to being complementary. Like, you probably can’t combine fire and water, unless you’re okay with the result being like steam or something, but you can be creative in how mages work together.

Finally, although this is specifically for my home rules, I think the structural nature of it lends it to being applicable in other non-level-based magic systems; e.g., in the GLOG (just replace references to spending inspiration with spending magic dice).