Ledger of the Lambs

Spells cast from exile have "Cascade."

Whenever a creature would die, exile it with
a soul counter on it instead.
Whenever a creature is exiled, put a soul
counter on Ledger of the Lambs.
Whenever there are twelve or more soul counters on
Ledger of the Lambs, each player may cast any
number of creatures they own in exile with a soul
counter on them without paying their mana costs.