If you mean the one in Underworld where the shield, mystic guard, spawns I do it like this:
Go through the entrance from Fire island, past the guards, past the slimes, past the acid slugs. Teleport over the broken wall to avoid going past the rotworms, turn left over the bridge, through the undead room to the trapped corridor.
Beyond that corridor is a gate and steps down to a beach. At the top of those steps I cast an earth elemental, then stealth down the steps and shadow jump to the island while the earth ele occupies the kraken.