Black Tom was born in Dublin. He is the cousin of Sean Cassidy, Banshee, member of the X-Men. His original principal power was that he could generate blasts of heat through a wooden medium, such as the shillelagh that he often carries. He has a rivalry with Sean, mainly because Sean won both Cassidy Keep, their estate, and the family fortune from Tom in a game of dice. They were also rivals for a woman named Maeve Rourke, whom Sean married. While Sean was away, working for INTERPOL, Maeve gave birth to their daughter, Theresa. Not much later, Maeve died in an IRA bombing. With no means to contact Sean, Tom took care of Theresa. When Sean returned to learn of his wife’s death, he was devastated. Before Tom could even tell him of the existence of his daughter, Sean lashed out at Tom with his sonic scream for not having taken better care of Maeve. While Sean flew away in anger, Tom fell into a chasm, breaking his leg as a result of the attack, which left him with a limp. Angrily, Tom swore to make Sean pay and vowed to never tell him about his daughter, raising her himself instead.
Later Tom became a criminal and came into conflict with the law and was apprehended. While serving time in prison, Tom met and befriended Juggernaut. The two became close friends and allies, and worked together on missions. As part of his revenge scheme against Sean, Tom murdered a lawyer ally of Banshee. Black Tom and Juggernaut then took Banshee and the other X-Men prisoner at Cassidy Keep. He was defeated in a duel by Banshee. Black Tom and Juggernaut next hired Arcade to kill the X-Men. On a mission in San Francisco with Juggernaut and Theresa (now under the codename Siryn), Tom encountered and fought the original Spider-Woman, along with several of the X-Men. This conflict ended in Black Tom's temporary capture. While in custody, Black Tom exonerated Theresa of responsibility for her crimes and wrote a letter to Sean explaining who she was. The X-Men brought Theresa back to their headquarters, where she was joyfully reunited with her father. Tom next sent the Juggernaut to abduct Madame Web, observing Juggernaut's battle with Spider-Man from afar. Black Tom was briefly endowed with half the powers of Juggernaut by the Ruby of Cyttorak. He then teamed with Juggernaut against Spider-Man and the X-Men. Black Tom next took Gideon and Sunspot hostage on behalf of Arianna Jankos. He used an interdimensional teleporter to return the Juggernaut to Earth. He then battled Siryn and her teammates in X-Force. Cable shot Tom, and Deadpool took Tom to Mr. Tolliver.
After being shot by Cable, Tom was taken to France, where doctors grafted a wood-like substance onto his wounds, healing him and allowing him to channel his bio-blasts directly through his fists. Unfortunately, due to a genetic virus the substance spread over Tom's body, and only the mutated cells of the mercenary Deadpool (due to his healing factor) were able to help Tom stop the spread of the plant growth. The effect of Deadpool's cells did not last for long. The spreading began again, to the point where Tom was completely composed of plant matter. As a result, his powers included control and manipulation of all manner of plant life, to the point where he could make plant doppelgangers of himself, or anyone else. He was completely insane as a result. During this time, Black Tom resurfaced as a member of the latest incarnation of the Brotherhood of Evil Mutants. Earlier, Juggernaut had infiltrated the X-Men for him as part of the Brotherhood's plan, though Juggernaut slowly changed during his time with the X-Men, mostly due to the positive influence of the young boy Sammy Paré. Juggernaut rejoined the Brotherhood, secretly planning on turning them when the time was right. Sammy stumbled upon the group, and assuming that Juggernaut was betraying the X-Men, started lashing out. In retaliation Tom brutally murdered the boy, causing Juggernaut to attack Cassidy, dismembering him. Due to Tom's new plantlike physiology, this did not hurt him. Juggernaut managed to escape and warn the X-Men, while Black Tom led an attack on the X-Mansion. Besides killing the school's cook, their mission was a failure. In the end Xorn sucked Black Tom and the rest of the Brotherhood into a black hole.
After M-Day, Black Tom woke up as a human again, losing his secondary mutation but possibly still retaining his old powers, along with his sanity. The organization Black Air hired Tom to attack the new incarnation of Excalibur, of which Juggernaut was now a member. Though he easily defeated the others, Juggernaut confronted his former friend and convinced him to turn himself in for the death of Sammy, Tom showed remorse for killing the child.
Powers and Abilities
Bio-Organic Thermokinetic Blasts: ability to generate blasts of concussive force or heat by using wood as the focus for his power; typically a wooden shillelagh. Following genetic engineering, Cassidy can channel the energy he generates directly through the parts of his body that were grafted to a wood-like substance.
Since his transformation into a plant-like being:
Plant Growth (formerly): Cassidy could grow to immense size.
- Superhuman Strength
- Healing Factor: could regenerate damaged or destroyed body parts with great speed.
Chlorokinesis (formerly): He could also mentally control all plant life within his vicinity.
- Plant Consciousness: could distribute his consciousness amongst plants he controlled.
- Life-Force Absorption: Cassidy could drain the life force of organic beings.
Genetic protection: Black Tom is highly resistant, if not immune,to Banshee and Siryn's sonics, and they are similarly protected from his bio-blasts.
His 'shillelagh' is a wooden club.