When Vault Oasis enters the battlefield, sacrifice it unless you pay 1 life.
: Add or to your mana pool.
: Add to your mana pool. Put Vault Oasis on top of your library.
When Vault Oasis enters the battlefield, put a -1/-1 counter on target land.
: Add 
or 
to your mana pool.: Add 
to your mana pool. Put Vault Oasis on top of your library.
