Blackwind

After finally leaving the Maelstrom Military Base, you will be in a short outdoor level. At the end of this, you will encounter your first Black Mode enemy. This guy absorbs a ton of damage and can deal devastating blows if you get too close, so circle and strafe to take him down (hopefully you've upgraded your Mech blasters). When he finally falls, he will drop a B-Wolfrium upgrade. Once you pick it up, you will learn the ability to enter Black Mode by pressing +. This slows time and makes you very over powered for a short time frame. Trophy will unlock the first time you use your new power.

As a side note, the game tells you to collect Red Orbs to recharge this ability, but there are no Red Orbs. It charges slowly as you deal damage and kill enemies. The meter is in the upper left corner of the screen, a red ring that forms around your character icon. When it's a full circle, you can activate this ability.