Arid-wood enters the battlefield tapped unless you pay .
: Add or to your mana pool.
Sacrifice Arid-wood: Add or to your mana pool.
: Arid-wood becomes a 2/1 white and green Knight creature until end of turn. It's still a land.
.
: Add or 
to your mana pool. or to your mana pool.: Arid-wood becomes a 2/1 white and green Knight creature until end of turn. It's still a land.
