Atem's Homecoming is a staff, an artifact with no stats or vanilla equivalent that is only used for its ability. Like all artifacts, it can be obtained from Pharaohs in Pyramids, breaking a Godforged Block (Unaligned or of the god), and extremely rarely from crates and Relic Ore.
Return: Teleports you back to your spawn point
Right clicking will immediately put you back to your spawn point. Note that if you are in another dimension than your spawn point, Atem's Homecoming will put in the same relative position in that dimension as your spawn point would be in its dimension. Beware, this can lead to getting stuck in walls, or teleporting straight into a pit of lava if you use it in the Nether while your spawn point is in the overworld.