Insidious Roots

Creature tokens you control have "{T}: Add one mana of any color."
Whenever one or more creature cards leave your graveyard, create a 0/1 green Plant creature token, then put a +1/+1 counter on each Plant you control.

Sakura-Tribe Elder

Sacrifice this creature: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Greater Good

Sacrifice a creature: Draw cards equal to the sacrificed creature's power, then discard three cards.

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.

Fiend Artisan

This creature gets +1/+1 for each creature card in your graveyard.
{X}{B/G}, {T}, Sacrifice another creature: Search your library for a creature card with mana value X or less, put it onto the battlefield, then shuffle. Activate only as a sorcery.

Birthing Pod

({G/P} can be paid with either {G} or 2 life.)
{1}{G/P}, {T}, Sacrifice a creature: Search your library for a creature card with mana value equal to 1 plus the sacrificed creature's mana value, put that card onto the battlefield, then shuffle. Activate only as a sorcery.

Eldritch Evolution

As an additional cost to cast this spell, sacrifice a creature.
Search your library for a creature card with mana value X or less, where X is 2 plus the sacrificed creature's mana value. Put that card onto the battlefield, then shuffle. Exile Eldritch Evolution.