Keeper of the Old Lords

Whenever Keeper of the Old Lords enters the battlefield each opponent discards a card.
Whenever a card is discarded, until end of turn noncreature spells cost X less to cast where X is
the converted mana cost of a discarded cards.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its
owner’s control with a -1/-1 counter on it.)