Delve Into Caverns

Landfall - Whenever a land enters the battlefield
under your control, put an Exploration counter
on Delve Into Caverns.
Remove three Exploration counters from Delve
Into Caverns, sacrifice Delve Into Caverns:
Create two 2/2 black Spider creature tokens with
reach. Then you may sacrifice a creature. If you
do, create two 2/2 black Spider creature tokens
with reach.