Tzeentch's beastmen twist reality as they themselves are twisted.

Tzaangor Shaman

Flying
Sorcerous Elixir — Whenever this creature deals combat damage to a player, copy the next instant or sorcery spell you cast this turn when you cast it. You may choose new targets for the copy.

Warhammer 40,000 Commander

Flying
Sorcerous Elixir — Whenever Tzaangor Shaman deals combat damage to a player, copy the next instant or sorcery spell you cast this turn when you cast it. You may choose new targets for the copy.

If Tzaangor Shaman deals combat damage to a player more than one time in a turn, perhaps because it has gained double strike, its delayed triggered ability will trigger that many times when you cast your next instant or sorcery spell this turn.