Collaborative Campign Building

Having players populate aspects of the campaign is always fun.  So here are some mechanics.

Whenever the GM likes (for example at the beginning of a campaign) or players like (for example they really want a location to exist), a player gets to describe something - an NPC, location, group, item, whatever. Keep in mind this has much potential for abuse, so don't be a jerk about it.

The player describes as much or as little as they like.  Then roll 2d6+something vs the GM's 2d6+Plausibility.

The +something will be based on what the description is about and how they know about it.  The GM should choose the appropriate attribute modifier.  Players may not Give It Their All (spend END to improve the roll).

Plausibility is a modifier from +0 to +6 based on the description and how reasonable this sort of thing would be. The GM needs to also not abuse this, so don't be a jerk to deny players cool things and quash creativity. The player does not get to know the results of the description.

Plausability
0: Likely
1: Reasonable
2: Probable
3: Possible
4: Imprrblable
5: Unreasonable
6: Unlikely

Results based on the Player's Roll (no conditional successes):

Result	Description Effects
Legendary Success	Exactly as described, and possibly even better.
Critical Success	Pretty much as described.
Success	Mostly true, but the details are a bit muddy.
Failure	Partially true, but one key factor is significantly different.
Critical Failure	Just plain wrong, possibly false.
Legendary Failure	Not only wrong, but wrong in a way that could be of significant danger.

In any case, the players can see the player-side roll results to get a feel for how strong this description they've provided is.

A Sweet Example
Tyler the Templar really wants to root out a Doomsday cult to impress his superiors in the Guild of Defenestration.  The GM asks about the cult, and the description is as follows:

The Siblings of the Red Dawn believe that the Others were sent to cleanse the world of sin, and the Dome stops them from completing their mission; if Haven is destroyed the world will be at peace. They have a prophet that is rising in power.

The GM thinks this is Likely (Plausibility 0).

Result	Description Effects
Legendary Success	The Red Dawn is ripe for a schism as their prophet is making several members uncomfortable. With a little nudge the entire cult will collapse in on itself in a very public display.
Critical Success	Pretty much as described.
Success	The prophet is actually a MirrorTwin from the Underworld, driving the cult to destroy the Dome so he and his brethren can run rampant in the World of Light
Failure	The cult actually has a plan an infiltrated the Magistarium!
Critical Failure	The Red Dawn are a cult that worships a barely-living Patchwork Daemon that babbles incoherent gibberish the cult takes as fact.  Their goal is to topple the Church of Eternal Light and humiliate the Templar.
Legendary Failure	The Red Dawn is actually a corrupt sect of the Hammers that have several ties to figures of political influence. They wish to bring down the "Culture of Strife" caused by the nobility and the influence of the Magistarium, but their schemes are mostly talk.  They are effectively a social club with meaningless rituals, but getting involved will cause the PCs some serious strife within Haven.