Artifact Key

Artifact Keys can be obtained by killing the boss (Hydra/Drake) on a Power Stone island, all players in the area around the boss will obtain a key directly into their inventory when the boss dies, they can then be transferred to other storage/players.

All Artifact keys have a 2 Hour decay timer, but can be used to activate the Power Stone Altar on any power stone island.

So a good tactic would be to kill a Hydra on D12 and then sail it to another Power Stone island.