Endless Ranks of the Tyranids

Enchant land you control.
Enchanted land has "{t}: Add {1}{s}"
At the beginning of your upkeep, create a 0/1
Spore Mine creature token with flying or if you
control seven or more lands create X X/X black
Tyranid creature token. Where X is half the
number of lands you control, rounded down.
Spore Mines you control have "{t}, Sacrifice this creature: Add {s}".