WOIN Cooperative Spellcasting


One thing that I love in stories and in the Elements of Magic supplement that the O.L.D. magic system was inspired by is the idea of rituals and cooperative spellcasting.

At the moment the closest we have to the idea of rituals in 1.2 is using long casting times. This kinda helps some flavor a little as it makes it feel like preparation can help a caster do stronger things, but it's pretty vague on the details.

If we look back at the 1.1 elements of magic chapter extracted to its own book it still has rules for what it calls rituals, where a caster can spend money to pay for the mana or give bonuses to casting, and someone with no MAGIC score can use LOGIC with  alchemy instead.

This is good, and I like it, but it doesn't really accomodate multiple casters working together or with careful preparation to perform great acts of magic.

I've purchased the Future Fantasy Cooperative Spellcasting rules from DriveThruRPG but it doesn't scratch the itch for me. It's a very specific flavor for it that isn't what I usually want for my games.

The two basic ways I am thinking of having this work is by using two different core mechanics of the game: simple additive tasks, and simple extended tasks.

These two also tie back into the Elements of Magic: Lycean Arcana rules for ritual casting. Simple additive tasks are like led rituals, and simple extended tasks are like communal rituals.

So for a simple additive task, casters add their MAGIC scores, and the single person who leads the spell now has this effective magic score and their own skill and equipment to a single dice roll that ignores their maximum die pool. This effective magic score sets the maximum spell MP that they can attempt to cast, as normal, and each caster cannot contribute more MP to the spell than their actual MAGIC score, and the full MP cost of the spell needs to be spent, as normal.

I leave it up to the GM on how characters contribute mana, maybe they have to touch the leader, maybe they have to be within 30' of someone else in the ritual. Maybe they need to see the caster. Maybe they just need to contribute mana at the right time. Maybe they have to cast a "blank" spell paying for range to get to target the caster and the extra mana is contributed to the spell (this way is likely to result in wasting a lot of mana, maybe this is what you want).

This type of spellcasting can work, but is fundamentally more risky than a single spellcaster casting the spell. Someone at an appropriate grade to cast a spell of the MP cost desired will usually have higher skill and better equipment than the leader of the ritual, leading to failure more often than a higher level spellcaster would.

Then, for a simple extended task, I would probably introduce a different DC for spellcasting, maybe 3 + MP instead of 10 + MP, and increase the maximum spell MP a caster can use based on the time increment of the extended task. Maybe +5 for quick, +10 for minor, +15 for major, +20 for extensive, and +25 for epic. Then at each time increment any caster who is contributing to the spell expends their MAGIC score in MP, and makes a check.

Once the required successes are hit, the spell is cast. Once the required failures are hit, I'd probably introduce spell mishaps. Then I'd make it so that any mage who starts to cast a spell this way must see it through to completion. Each time increment they roll and spend the MP. If the caster has less MP than their MAGIC score they expend the rest, make a roll with the DC increased by how many MP they fell short, and gain a persistent level of Fatigued. They will then be ejected from the spell and cannot rejoin it, even if they regain MP. For a minor or lesser extended task, this probably just ends the spell if the last caster is ejected from the spell, but for a major or greater one it probably creates a mishap.

For this type of communal spellcasting each contributing caster is making a roll all their own, so I'd probably mandate that they be within range of both the target and another caster in the ritual to contribute. Leaving that range probably either triggers a mishap, or drains the leaving caster and gives them a persistent level of Fatigued.

I'm thinking required successes should baseline at 2, and maybe give +1d6 to each contributing caster for each extra required check?

I haven't done any math on all this to see whether any of it might be close to balanced. Probably not, I'll need to tune it a lot.

That wraps up my first thoughts on a cooperative casting system for the game, what are your thoughts?
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Adding a couple extra thoughts, the modifier from extra required successes should probably cap at the caster's skill pool.

And perhaps all the MP bonuses should be shifted up by 5 and add a new "momentary" extended task which has a time increment of like one or two rounds instead of one minute which gives +5. That way a combat encounter could be built around protecting casters trying to finish a ritual using these rules.

Also maybe these rules could be combined, with each caster contributing to the simple extended task having their own simple additive task to allow many archmages guiding many many weaker spellcasters in truely huge rituals.

I've been thinking about this for a while.
I really love the idea of collective and collective ritual casting, is great both for worldbuilding and as a tool for interesting encounters.

I'd add a couple of considerations:
  • creatures with 0 MAG can still provide 1 MP each per day. This allows farmers, commoners, and general non magically skilled npcs to contribute to a spell. I like the idea that towns can engage in public holidays and rituals to protect the village, improve crop yields, etc, and everyone can actively contribute. On the other hand, a group of cultists without any spellcasting training could still participate in a demon summoning ritual.
  • I'd like to reintroduce material components, maybe in a semi freeform fashion: the component must be somehow linked to the spell, and it's value (in GP for inanimate parts, or in terms of MDP of the creature that supplied it) adds MPs thus making the spell cheaper to cast
  • Maybe it could be fun to have collaborative casting to not fail because one member is stopped or incapacitated. Maybe the others will have to strain even more in order to maintain control of the spell, or maybe a new leader will have to kick.

For how to combine I'll need to give some more thought, as well for the balancing.
I guess a lot of the balancing will also depend on what kind of feel one wants to give to this casting fashion. I'd love collaborative and ritual casting to be powerful, so that mythical/high fantasy feats of magic can be performed.

Since it seems we're going in quite the same direction, would you like to collaborate or brainstorm a bit more?

An additional thought: maybe we need to add some soft cap on how many MPs can be contributed depending on the number of participants: I like the idea of a small village engaging in a spell to improve their crops, but a city with hundreds or thousands of participants could cast a stupidly high MP spell.
So maybe something like:
1-10 participants add up to their MAG each (min 1 each)
10-100 add up to 1/8th of their MAG each (sum MPs, then divide, then round down)
100-1000 add 1/16th and so on

I need to check this kind of scaling makes sense, the idea is that the marginal contribution is still positive but decreasing the more participants are there.

Alternatively, the max number of participants depends on some kind of skill of the leader, and we can have a hierarchy of groups, so that we have something like 1 arch-druid, 5 high-druid, 25 druids/priests and 125 commoners


Yes, I'd love to brainstorm more together.

Also I don't think a whole city would be able to do all that much more than a small church or something would be able to do, because part of the idea is even if they can contribute 1 mana, it's still a simple additive task, so adding 0 to the score isn't gonna help beating the spellcasting DC. So if there is a soft cap to be added, then it only applies to e.g. a city of grand elves or gnomes or something where everyone has a notable magic score.

That said, I was more or less thinking that the soft cap would be created by the GM's choice of how mana is contributed. If all the participants have to touch the caster then you can only fit so many people around the caster at once. Your listed soft cap would just be a limit for your choice of how MP is contributed.

Also while I'm thinking about it, there's also kinda a soft cap on spellcasting in general because eventually the amount of score increase you need for a die increase is so great that you'll never be able to cast anything close to a spell that's actually at a level equal to the sum of all the magic scores.

The hierarchy thing was also something I wanted to do somewhat with simple additive tasks being used to do the checks for the extended task.

Yes, I'd love to brainstorm more together.
I'll DM you :)
Also I don't think a whole city would be able to do all that much more than a small church or something would be able to do, because part of the idea is even if they can contribute 1 mana, it's still a simple additive task, so adding 0 to the score isn't gonna help beating the spellcasting DC. So if there is a soft cap to be added, then it only applies to e.g. a city of grand elves or gnomes or something where everyone has a notable magic score.
This is a valid point, and actually carries through for a city of grand elves or a wizardry school, since there would be someone that needs a skill+equipment+attribute high enough to have a chance to cast that spell.
So even if in theory there are 1000MPs available, a 1000MP spell will have RAW a DC of 1010...

If anything we may need to check that the DC scaling isn't so steep to cancel out any potential benefit of having a higher MP cap in the first place

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