Origin

He teamed up with Juggernaut on several occasions. He was also a member of the Brotherhood of Evil Mutants.

Later, his chemistry, physiology, and morphology were radically changed, and he became a humanoid plant form capable of living in several different bodies and infecting folliage and trees to make them a part of his body. This made him difficult to restrain or destroy because it was nearly impossible to destroy every part of his body, as much of it could be kept underground, and because he could invade other plants with his life force to add them to his own body. While in this form, he was also able to siphon off the life energy of living beings by sending specialized tendrils into their body cavities. However, the process seemed to have affected his mind, and he wasn't in full control of himself.

During this time, he, along with Mondo, attacked his cousin Banshee's group of charges called Generation X, kidnapping them and imprisioning beneath the ocean in a self-contained pod. He thought he'd thought of everything, but he forgot Hollow, who sliced him in half, seemingly killing him, until he later resurfaced. Penance's attack managed to loosen his will around the pod at the bottom of the ocean such that the kids of Generation X were freed.

Powers

Originally, his principal power was Bio-Organic Thermokinetic Blasts, generating concussive blasts of force through any wooden medium. He typically carries a shillelagh, a traditional Irish wooden fighting stick. He is immune to Banshee's sonic powers, and Banshee is immune to his blast power.

Former Powers

Planet Growth: Cassidy could grow to immense size

Superhuman Strength

Healing Factor: regenerate damaged or destroyed body parts with great speed.

Chlorokinesis: He could also mentally control all plant life within his vicinity

Planet Consciousness: distribute his consciousness amongst plants he controls.

Life-Force Absorption: Cassidy could drain the life force of organic beings.

After M-Day, in which most mutants lost their powers, he lost his alterations and his human form was restored, though he still retains his original abilities.

Characteristics

Height: (currently) 6'0"; (formerly) Variable
Weight: (currently) 200 lbs.; (formerly) Variable

Eyes: Brown

Hair: Black

Unusual Features: Up until recently, he was made up out of plant matter.