(Slagheap Catacombs isn't a spell.)
Slagheap Catacombs enters the battlefield tapped unless you pay .
, : Tap target artifact with converted mana cost X or less.
: Add or to your mana pool.
Sacrifice Slagheap Catacombs: Add or to your mana pool.
.
, 
: Tap target artifact with converted mana cost X or less.: Add 
or 
to your mana pool. or to your mana pool.
