Meren of Clan Nel Toth

Whenever another creature you control dies, you get an experience counter.
At the beginning of your end step, choose target creature card in your graveyard. If that card's mana value is less than or equal to the number of experience counters you have, return it to the battlefield. Otherwise, put it into your hand.

Eternal Witness

When Eternal Witness enters the battlefield, you may return target card from your graveyard to your hand.

Black Sun's Zenith

Put X -1/-1 counters on each creature. Shuffle Black Sun's Zenith into its owner's library.

Rise of the Dark Realms

Put all creature cards from all graveyards onto the battlefield under your control.