In the process of creating a homebrew system, I have run into the problem of my players wanting to be able to combine their spellcasting prowess in a show of superiority and might ( and perhaps a bit of awesomeness ). I have not, however, found solid mechanical way of adjudicating this. I have a "standard" combine actions bonus, but that does not seem to carry over the flavor of two mages summoning up their will and throwing "earth+fire=magma bomb" sorts of spells out to slug their victims enemies with, both in off-the-cuff spontaneous casting and forewarned-is-forearmed rituals.

I have looked through a few systems, but have yet to find any with decent - or even existent - multiple caster or combined magic rules. Red Wizard of Thay in DnD 3.0/3.5 is one, Ars Magica 4e had what amounted to little more than a footnote, both oWoD and nWoD Mage was of no help, ditto on Thaumaturgy from oWoD Vampire. I have thought to double check Dresden Files RPG, but loaned out my books (not that I recall anything of the sort from there).

I find myself out of ideas to try and books to search.

  • \$\begingroup\$ How was nWoD Mage of no help exactly ? I seem to remember rather explicit rules about this in the core book... \$\endgroup\$
    – Nigralbus
    May 20, 2013 at 9:01
  • \$\begingroup\$ @Nigralbus Indeed there are, pp129, "Group Rituals". The short is that "[It] is handled like any other action where characters combine their efforts...". This does not work for my system. \$\endgroup\$
    – Phill.Zitt
    May 20, 2013 at 10:59
  • \$\begingroup\$ Yeah, I figured what you asked wouldn't really work after thinking about it a little. \$\endgroup\$
    – Nigralbus
    May 20, 2013 at 12:19
  • \$\begingroup\$ Hey man. We don't really do list questions here; a good RPG.SE question should have a single best answer. If you were to put in requirements as to what "good" combined casting means to you, then perhaps. \$\endgroup\$
    – mxyzplk
    May 21, 2013 at 11:28

4 Answers 4


Wizard's Communion in Ars Magica is the only way to pull of some of the obscenely high rituals promised by the system.

The rules for Wizard's Communion (A Rego Vim general spell) allow a number of casters to reduce the difficulty of a ritual according to a set number of guidelines. The spell is difficult, and can get very expensive, but allows commensurate rewards in the reduction of difficulty. It is the most elegant participation means that I've seen, such that my group actually uses it.


Pendragon 4th Edition has rules for group casting. (but it's the only edition with magic rules.)

Burning Wheel has some in Magic Burner.

GURPS Magic for 3E had some; GURPS Fantasy for 1st ed did, too.

The Fantasy Trip has them in Advanced Wizard. GURPS Fantasy 1E was pretty much the same magic system...


I see two ways you can go here

  • Rigid system with pre-defined effects and math to combine them. You can find a lot of element spells in GURPS Magic and adopt something akin to GURPS advantages(and mods) math to represent spell combinations.
  • Or more streamlined game where system is abstract enough to ignore everything beyond casting difficulty. PDQ# or Lady Blackbird will work fine, Dont Rest Your Head will be... amusing. Or you might want to read Marvel Heroic Roleplaying, where Cortex+ system makes exceptional job of representing hero powers.

Marvel Heroic Roleplaying will be the system I most probably go with, so I will take a moment to explain it a bit:
Game represents powers (actually everything) with a die level, quite alike to Savage Worlds. But instead of strict rules, it allows you to combine everything that applies to your action in a single roll: Flight d8 + Teamwork d6 + Lasersight (of partner sitting on my back) d10 + My Wingsuit d8 to shoot down that terrorists' plane.
You choose two dice from the roll to be an effort and one die (this time die size, not the face) to be an effect. If my previous example rolls 6,5,5,8, I'd take 14(6+8) as my effort and d10 (rolled 5, meh) as my effect size, be it a damage or Fate-like scene aspect. Without a partner my best damage would be a d8.

There is a lot more to the system, rest assured, it is very smart and unconventional in a good way.

My second thought is: Dogs in a Vineyard could be a hit/miss depending on what kind of scenario you're going to play.


Rolemaster has some ritual group-casting rules in Rolemaster Companion II, but I don't know if this carried onto the RMSS.

This is a way of casting spells above your level or that you may not even know; it's a one roll resolution (RMC2 adds a success table for this, and what's Rolemaster without a table?)

Difficulty is modified by Ritual skill, spell level vs. caster, if you know, mitigating factors (phase of moon if appropriate and so on) plus assisting casters add a bonus to the roll, depending on their skill/success

If you want to look at this as an option you'd probably get a good idea just from looking at RMC2


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