billd91
Not your screen monkey (he/him) 🇺🇦🇵🇸🏳️⚧️
Are you certain the creature has to take the -20 to be able to move? That capability is bestowed by improved grab itself in the last sentence of the ability, far removed from the rules that govern taking that -20.
I'm certain enough to rule it that way and not have any doubts that it's more fair and realistic than the alternative.
Taking the -20 allows the creature to maintain the hold without being considered grappled. If he doesn't take it, the conditions of being grappled apply - including the one that says they can't normally move. Otherwise, the creature is stuck in the grappled status and has to make a grapple check as a standard action to move half his rate.