Peladus looks surprised when he reads the inscription, then turns to the others and whispers, "There must be spellcasters here. This text says, 'If opened up you wish to see, then fed with magic must I be.' Now that either means that there's a lot of magic around ... or else that spellcasters are few, and in positions of control. Either way, I think I can open the gate, if you're ready?"
If people indicate that they're prepared, Peladus casts Ray of Enfeeblement on the dragon. If nothing happens, he'll frown, then take out a potion of Cure Light Wounds and put that in the dragon's mouth.