Salvage Arm
Salvage Arm is a Boss artifact for Isaac that gives you Energy whenever you destroy a Midrow Object.
Clarification
A midrow object is considered to be destroyed by the player if:
- 1. An attack by the player destroys a Midrow Object (even automatically triggered by Strafe, Payback, or Safety Override)
- 2. The player's launched midrow object is destroyed by a collision with an existing midrow object
- 3. An existing midrow object is destroyed by a collision with a player-launched midrow object
- 4. Sport Orb is hit by the player into an existing midrow object, destroying it
Notably, launching a midrow object into an existing object, with neither (or both) having a Bubble Shield, gives you 2 Energy with this artifact.
Strategy
Salvage Arm provides Energy, a powerful resource, when destroying a midrow object. It certainly has some situational value against enemies that use missiles against you. Notably, launching a midrow object into another midrow object is 2 Energy.
But this artifact can prove to be quite situational most of the time, as not all enemies use midrow objects. When enemies don't, you have to destroy your own midrow objects for this to be of any use, and even in the ones where enemies do, only on the turns they launch midrow objects. So in practice, this artifact usually needs you to be using disposable midrow objects like Asteroids and Geodes to be worth your while. Even then, you'll need to be able to mass-launch midrow objects, and you'll need ways to use the bursts of Energy you'll get when this happens. Expensive cards that launch many rocks, like Large Boulders and Boulder Bundle, are essential to using this well, and if you have Books, Mineral Deposit and Rock Collection are also great helpers. Finally, Rock Factory is probably the best enabler of this card, giving you 2 Energy next turn when you line up your Missile Bay with an existing midrow object, or 2 Energy unconditionally if you can get 2 or more stacks of it. But even then, you'll need expensive cards and/or card draw (which Isaac doesn't have, mostly) to take full advantage. With Math.Max, it's possible to go infinite with this and two Small Boulders, or one Large Boulders A if you can get your deck down to 10 cards.
Its situational nature coupled with being a Boss artifact makes it fairly difficult to take most of the time in practice, though it can produce some unique winning strategies when it works.