Rigrop, Fungal Revitalizer

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Whenever a creature you control dies, gain X life, where X is that creature's toughness.

Whenever one or more tokens enter the battlefield under your control you may pay 1 life, if you do, put the top 4 cards of your library into your graveyard, then return a creature card from your graveyard to your hand.