Keeper of the Old Lords

First Strike, Vigilance

Whe Keeper of the Old Lords enters the battlefield, each opponent discards a card and target Great One gains hexproof as long as Keeper of the Old Lords is on the battlefield. Whenever a card is discarded, until end of turn, noncreature spells cost X less to cast, where X is the discarded card’s mana value.

Persist (When this creature dies, return it to the battlefield under its owner's control with a -1/-1 counter on
it.)