Crystal Monsters versus Cursed Seal of the Forbidden

[Cardinal]

Would Crystal Beasts be effected by Cursed Seal of the Forbidden or Spell Vanishing, when they become spell cards by there effects?.

 

[Entropy]

You can't chain any of those to the Crystal Beast's effect. First, it's not chainable. Second, it's a monster effect, not the activation of a Spell card.

 

[Dillie-O]

Well put Entropy. If this still confuses you at all, think about Dark Necrofear. It's effect triggers and activates as a monster, but when it resolves, it becomes and equip spell card.