Cloning Silvergill Adept

[CbStrad]

So let's say I have a {Silvergill Adept} on the board and throw a {Phantasmal Image}, copying it. Would I have to pay any additional casting costs since it enters as an Adept?

[Mlerner12]

No. You are casting Phantasmal Image, and not the Merfolk. You don't need to pay additional costs. However, it enters the battlefield as the Merfolk thing, so you do draw a card. I cannot find an additional rule to cite this.