Champions From Beyond the Rift

Let expanse contract, eon become instant!
Champions from beyond the rift, heed my call!

A vast arcane circle emerges from under target player-character’s feet. Along the outside are 7 empty circles which then erupt in pillars of light. Each summons a hero in their prime from across space and time.

This spell may only be cast when target character faces an enemy with CR greater than or equal to 4 times their own, alone. 

Suspend play until 7 other players are present, and have characters of the same level as the target character ready. Summon all 7 characters in a ring around target character. Resume play after all 7 characters are summoned. 

When this spell is cast, until either all player characters are at 0 hit points, or combat ends, no player characters may fully die, and no player characters may drop below 0 hit points. If a player character drops to 0 hit points and then is healed, they get a stack of exhaustion, up to a maximum of 4. 

Whenever combat ends, all summoned characters return to the exact place and time they were at before being summoned.