REGISTER TO REMOVE ADS
At first I was going to say with the trolls--since they probably would've found it and guarded it--but it's more likely the Keyholes would be wherever they would "look" the best for max dramatic effect. For example, I never thought it made much sense for Atlantica's Keyhole to be in Ariel's grotto. It would've made more sense if it had been in the far-out cavern where you fight giant Ursula. Logically, Arendelle's Keyhole would be anywhere on the mountain really, somewhere where people would be unlikely to stumble on it.I was thinking the troll's place or somewhere under the fjord.