Gathan Raiders versus Mother of Runes

[Ace/Homebrew]

While a morph, Gathan Raiders is colorless. Unmorphing* it does not use the stack.
Mother of Runes gives target creature protection from the color of your choice until end of turn.


Battlefield:
I have a 2/2 colorless morph which is a Gathan Raiders. My opponent has an active Mother of Runes and a Grizzly Bear.

I attack with my morph...

Question: If my opponent blocks with the Grizzly Bear, is there a way that I can unmorph my Raiders, making it a 3/3 or 5/5, without giving my opponent a chance to activate his Mom to give the bear pro-Red?



* What is the correct term here? When I cast it, I 'play a morph'. When I pay the cost to turn it over am I morphing it? Unmorphing it?

[Koby]

While unmorphing doesn't use the stack, you can only activate it when you have priority. After activating the morph, priority is checked with both players before damage is dealt. Your opponent would have the opportunity to give protection with Mother of Runes before damage would be dealt.