Selkie Skin Magic item – roll or not roll?
Recently my players visited the Shrine of the sea goddess ( https://plus.google.com/101199869016634749008/posts/QVJZPv58n85 ), and stared into the deep abyss. A lot of GM hold was gained. (Se the custom move in link)
As a concequence the halfling thief Thalda was compelled by the abyss to steal the shrine-keeper Sigyn Volvas seal skin cloak. This is a magic item inspired by “Billy Bones and his nautical nonpareils”, a selkie skin. We ended the session as they were about to be attacked by sea serpents, and I might invoke one hold to get the thief to wrap the cloak around her and dive into the water – placing her in a dangerous position but also revealing the cloaks power to turn you into a seal.
This is a potentially quite powerful magic item, and as described it just turns you into a seal: “When you wrap yourself in the selkie skin, you turn
into a seal for as long as you stay in salt water.”
Is this fine, or should I make a custom move with a roll, with 7-9 being something like “it only lasts a little while” or “you embrace your new form a little too much”?
Current gut feeling: save those for the inevitable Defy Dangers involved in misusing this item in creative ways.