Piercer
Piercer is an artifact that gives your first attack pierce each turn.
Strategy
Pierce is a very self-synergistic mechanic - it's at its best when all of your attacks pierce, so that your enemy's Shield doesn't matter. (On the other hand, a mix of piercing and non-piercing attacks isn't any better than all non-piercing in most fights, since your enemy's Shield will still find use in blocking your non-piercing shots). So that makes this artifact at its best on defensive ships that typically don't attack more than once per turn - that way, Piercer will apply to most/all of your damage and essentially negate your enemy's shield. It can also be good with Drake on your crew if you've drafted a few piercing cards - just be sure to play a non-piercing attack first so that this artifact gets put to use, then play your natively-piercing attacks.
It's particularly nice in a Corrosion-based build for this reason, as corrosion damage natively pierces, and those builds tend to be defensive, not attacking more than once per turn. Acid Cannon really likes this artifact.
Piercer can get some incidental use in bypassing Armor and bubble shields if your ship really is meant to attack multiple times each turn. It can also be very effective against a few specific enemies with little hull but big Shield, most notably Needler. But, overall, it's pretty underwhelming in this case.