Talk:Sky Castle of Drago Phantom Thief, "Lebla Maurice"/@comment-44783469-20200103050328/@comment-26684750-20200103051545

The fact that the last sentence says  "You may only cast "Sky Castle of Drago Phantom Thief, "Lebla Maurice"" once per turn." should probably tell you that you do, in fact cast it.

The effects of the spell are split into two. The first paragraph is a continuous effect that is applied if the conditions are fulfilled (one of which requires it to be in your buddy zone). The second paragraph, starting from the words, "If your buddy is a spell, ", is a singular activation effect that happens when you cast it.