Geralf's Laboratory

Geralf's Laboratory enters the battlefield with three Research counters.
At the beginning of your upkeep, you may place the top card of your library into your graveyard and place a Research counter on Geralf's Laboratory.
{x}: Exile a creature card from your graveyard and place an X/X Blue Zombie Horror creature onto the battlefield, where is X is the number of research counters on Geralf's Laboratory.