Kaishu, Inveigling Oni

As an additional cost to cast this spell, you may sacrifice any number of creatures. This spell
costs {1} less to cast for each Samurai creature sacrificed this way.
Other Samurai creatures you control have double strike.
At the beginning of each end step, if one or more Samurai creatures died under your control this
turn, you may pay 6 life. If you do, destroy target nonbasic land an opponent controls.