Riling Dawnbreaker

If you cast an omen card as an Omen, use only its alternative characteristics to determine whether it’s legal to cast that spell. For example, if you control Thundermane Dragon (“You may cast creature spells with power 4 or greater from the top of your library.”) and Twinmaw Stormbrood is on top of your library, you can cast Twinmaw Stormbrood, but not Charring Bite.

If a spell is cast as an Omen, its controller shuffles it into its owner’s library instead of putting it into its owner’s graveyard as it resolves.

If an Omen spell has one or more targets and all of those targets are illegal when the spell tries to resolve, it won’t resolve. None of its effects will happen, and it will be put into its owner’s graveyard. It won’t be shuffled into its owner’s library.