The Necropolis

Indestructable
{1}: Search for an "Acolyte" and put it into onto the battlefield tapped, then shuffle your library
{3}{t}: Search for an Undead creature and put it into your hand, then shuffle your library
This comes onto the field with 5 "Blight" counters.
Remove a Blight counter: Upgrade target building
Whenever a creature is destroyed, add a Blight counter to this card.