Black Hole Sun

Description
Sentry X-58 activates a Shield which reduces the damage taken, and absorbs a percentage of the damage (indicated by a purple bar under his health bar). It absorbs damage from environmental hazards (Solar Boss, Inferno Device, and Turrets) less efficiently. If the shield absorbs enough damage, it will end prematurely. Absorbed damage will start to decay after some time has passed.

Once the shield is expired, Sentry is able to shoot an aimable black hole out of his cannon, which flies in a straight line and will detonate after reaching maximum range or with a second press of the button. It will pull all enemies caught inside the black hole towards it for the duration, the pulling being strongest at its center. At the end of the effect, the black hole will explode, dealing a small amount of damage plus a bonus based on the damage absorbed initially.

Trivia
The name Black Hole Sun is likely a reference to a popular Soundgarden song of the same name.