Hunter Wings
Hunter Wings is a Boss artifact exclusive to the Artemis that makes its Wings Empty during the enemy's turn if you end your turn with 1 or more Energy.
Strategy
Hunter Wings essentially lets you trade 1 Energy for what's often worth at least 1 Evade, which is a great asset. It can often be worth more than that, especially against bosses, where it often lets you nestle in a hole in the enemy's firing pattern. When figuring out how best to manage your defensive economy in any given turn, you'll often find it's worth using this artifact, so don't forget about it!
It has synergy with other artifacts that reward leaving an Energy at end-of-turn, such as Ion Converter and Standby Mode, as it doesn't technically "use up" the Energy, so you can benefit from them all at the same time.
Against Buried(?) Relic in particular, you can use this to nestle against the right (or on Normal difficulty where your Cockpit isn't weak, the left) side and use it every turn. This leaves only one part of your ship exposed to its rightmost cannon, usually allowing you to focus it down before it can hit you too hard. Against The Cobalt, if you can stun its concussible cannons to the left or right of its main cannon, there's a 3 space wide gap to the left/right of its main cannon where you can hide, taking no hits at all.