Sword of Forge and Frontier's protection prevents damage from red and greeen sources. (And it also does a lot of other stuff thats not important now)
Questing beast reads:
Combat damage that would be dealt by creatures you control can’t be prevented.
So protection cannot prevent damage from questing beast
Sword of Forge and Frontier's protection prevents damage from red and greeen sources. (And it also does a lot of other stuff thats not important now)
Questing beast reads:
Combat damage that would be dealt by creatures you control can’t be prevented.
So protection cannot prevent damage from questing beast
Everything in this interaction works as intended