As long as the top card of your graveyard is a creature card, this creature has the full text of that card and has the text "{2}: Discard a card." {2}: Discard a card.
Enchant creature card in a graveyard When this Aura enters, if it's on the battlefield, it loses "enchant creature card in a graveyard" and gains "enchant creature put onto the battlefield with this Aura." Return enchanted creature card to the battlefield under your control and attach this Aura to it. When this Aura leaves the battlefield, that creature's controller sacrifices it. Enchanted creature gets -1/-0.
Crovax enters with four +1/+1 counters on it. At the beginning of your upkeep, you may sacrifice a creature. If you do, put a +1/+1 counter on Crovax. If you don't, remove a +1/+1 counter from Crovax. {B}: Crovax gains flying until end of turn.
This creature enters with X +1/+1 counters on it, where X is the number of creature cards in all graveyards. {2}{B}, Remove a +1/+1 counter from this creature: Target creature gets -1/-1 until end of turn.
Haste At the beginning of the end step, sacrifice this creature. At the beginning of your upkeep, if this card is in your graveyard, you may exile a black creature card other than this card from your graveyard. If you do, return this card to the battlefield.
When this creature enters, target player loses 6 life. When this creature leaves the battlefield, that player gains 6 life. {B}: Regenerate this creature.