Reckless

Reckless is a keyword ability designed for Gatecrash that provides an effect but at the cost of sacrificing the creature at the end of the turn.

Description
Design experimented with this mechanic for the Gruul guild. When you activated the ability on a creature (usually an upgrading effect), then the creature were sacrificed at the end of the turn.

This mechanic also was taken into account when designing Amonkhet, where the flavor was that you could essentially force the creature to do something that they might not want to do. It wasn't the creature making the choice but you, the puppet master behind the scenes. This sinister of a feel was more aligned with the top down design on Nicol Bolas world.

Finally, by suggestion of Jackie Lee, the mechanic was redesigned as exert.