When Ochobot was destroyed and gave BoBoiBoy the last of his powers, BoBoiBoy summoned Thorn, along with all the other forms in a blind rage. He then appears after Boboiboy uses Hepta split to defeat Borara once and for all, Boboiboy Thorn was one of the ones appearing from the split, he was seen using Ensnaring Thorns to wrap Borara in one of the floating island.
His appearance is somewhat the same as the other forms of BoBoiBoy with cropped black hair and the regular physique of a child, but BoBoiBoy Thorn possesses green irises and is clad in mostly green and black with his cap being fully black with a minor addition of neon green vine-like linings adorning the sides of his cap all the way to the bill. He wears the said cap with the bill turned to the left of his head. Unlike the other elemental split personas, BoBoiBoy Thorn does not appear to sport a jacket but instead, he wears a short-sleeved shirt with black coloring the upper part and green on the lower part of the shirt, with green pants adorned with black jagged, thorn-like linings at the sides. His shoes are a mix of green and black colors laced with white shoelaces. His insignia is placed at the front of his shirt, right under the hoodie. Accessories that mainly differentiate him from the other forms happen to be the green thorn-like studs on a green wristband worn on his left wrist and a black arm warmer (adorned with green studs) that covers all the way from his right forearm to his hand.
Unlike the other Elemental Forms, BoBoiBoy Thorn is might be very naive and is kind of a simpleton, just like Leaf.
Being the evolved form of BoBoiBoy Leaf, BoBoiBoy Thorn has similar and evolved abilities that BoBoiBoy Leaf has.
- Ensnaring Thorns (Akar Berduri) - This attacking power consists of thorny vines, lengthened to desire. It holds the purpose of binding one to place thus immobile them.
- Alongside BoBoiBoy Solar, BoBoiBoy Thorn is one of the only two elements where BoBoiBoy did not need the base form (in this case Leaf) to use that form.
- BoBoiBoy apparently loses the ability to use this form in the events of BoBoiBoy Galaxy, but Thorn's base form, Leaf, appears in Episode 5, hinting that Thorn will appear in the future.