Skaab Goliath

[Hakuu]

If there are no creature cards in th gy,
Can I still cast {Skaab Goliath }?

[Coffee Vampire]

Nope, sorry.

[Jroch314]

If it said "when it enters the battlefield" then you could.

[An Angry Fatman]

If it said "when it enters the battlefield" then you could.

If it said this, then you would be able to exile two non-existent creatures because it wouldn't be a part of the cost of summoning the skaab. Because you cannot meet both requirements of the cost, you would not be able to cast the skaab and it would be considered an illegal move.