Power of the Pyramid
Among the Tremere clan's most famous exploits are its great binding rituals over the entirety of the Tremere antitribu and the majority of the Assamite clan. No lone thaumaturge could accomplish such a feat. Only by sharing strength can the Tremere achieve the necessary might to create or resist such forces.
To combine thaumaturgical strength, Tremere Kindred can use a linking ritual. The Power of the Pyramid rite requires that each participant know and invoke the ritual simultaneously, and requires physical contact - so a group of Tremere, formed in a circle with linked hands, all chanting the same words in unison, indicates that the clan prepares fro a daunting task. Once completed, the rite allows the Tremere involved to gather their mental strength together so that they can multiply their power.
Perhaps because of its connotations, this ritual only works for Kindred of Tremere lineage. Other vampires might be able to learn it, but it would probably not do them much good.
This ritual requires the casters to fast for 24 hours before performing it. Additionally, one of the thaumaturges participating in the group must wear a brooch or pin made from mortal bone, which must pierce his flesh (though it need not be visible to the rest of the group).
System: Each Kindred involved in Power of the Pyramid must know this ritual and successfully cast it simultaneously - any failed castings simply exclude the individual from the circle but do not hinder other successes. Once complete, a single Tremere can break from the circle without nullifying the ritual, but if any others lose physical contact the ritual ends. So long as the ritual continues, all participants may freely share their Willpower. Thus, one Tremere could break freely share their Willpower. Thus, one Tremere could break from the circle, perform another ritual and draw upon the Willpower of all Kindred involved. Once a caster has broken from the circle, he cannot return and release someone else; from the circle, he cannot return and release someone else; that "lynchpin" is the only one able to move around freely.