Falthis

Falthis is a Nightmare Cat from an unknown plane, and a Mage's familiar.

To call all black cats bad luck is a gross exaggeration. That being said, if you summon Falthis as your familiar, you might want to watch your back. It's not like she doesn't have her perks. With Falthis by your side, dark magic will multiply in power and weaker foes are nowhere to be found. However, Falthis's connection to corrupting forces is so great that it tends to physically manifest on her current master. But as long as you're okay with a few malignant mutations, you'll find yourself partnered with a very cute kitty.