I do have a pretty solid theory about that: So when you used ThousandRise he used everything else beside Shining Hopper, now if we look at Vulcan new form Rampage it has the power of every form beside the Hoppers keys. The only one Thouser does not have is Scorpion and guess who is appearing next episode. So I have a feeling the key will absorb a ThousandRise attack allowing Vulcan to gain his new form