(Slagheap Garrison isn't a spell.)
Slagheap Garrison enters the battlefield tapped unless you control four or more enchantments.
Sacrifice a land: You gain 1 life.
: Add or to your mana pool.
Sacrifice Slagheap Garrison: Add or to your mana pool.
: Add 
or 
to your mana pool. or to your mana pool.
