Xolaani the Bloodweaver

Anytime another creature or equipment you
control is destroyed or sacrificed, put a +1/+1
counter on this creature. Counters remain on
Xolaani the Bloodweaver as it moves to any zone
other than a player's hand or library. When
Xolaani has 16 or more power, transform it.
Sacrifice Xolaani: Discover a Darkin equipment.
Choose Background The World Ender.