OOC: Here As a part of the Kah-Gash, the most powerful magical weapon in the Human and Demonata universe, Grubbs Grady is a magician even though he hid it from himself, and has large amounts of power at his fingertips, even when demons are not around. He was even able to hide his magic when Dervish probed into his brain, something that is supposed to be impossible. The exact extent of his powers is unknown, but he was able to severely hinder Lord Loss in Slawter while Dervish couldn't even cause Lord Loss to flinch. Also, the part of Grubbs' Kah-Gash, allowed him to transfom into a werewolf. The wolfen curse afflicted the Grady line (known before as Garadexes), when millenia ago one of the Garadexes bore children of one of the Demonata. This transformation heightened Grubbs' senses, made him become taller, broader and hairer, with superhuman strength. Some people have magic within them, however it usually remains dormant unless the person sees something magical like a demon attack, or uses magic in an area where lots of mystical energy is present, and they become aware that they have powers. From this the Disciples, (others that have become aware of their powers and answer to a magician known as Beranabus), can contact the person that has become aware and attempt to recruit them in to the ranks of the other Disciples to travel around the world and stop demons from passing into our Universe.
Most of the Disciples have very limited powers unless in the presence of the Demons or in the Demon universe. However, Grubbs managed to disable large security flood lights and turn concrete blocks to mud-like sludge so they can be scooped out of a wall in Slawter. However, there were demons close by at that point, so he may have been tapping into their magic. He does a few spells that are average in power but near the end creates a barrier that demons cannot pass, something which Dervish could not do. At first Grubbs believes he was only able to use magic in the presence of demons but at the end of Slawter he tests his powers, when not in the presence of demons and finds that he can make his reflection disappear and change light. Only a few people can use magic outside of the demon universe, and to be able to do it without training means that Grubbs is extremely powerful and is also a magician. Beranabus confirms this in Demon Apocalypse, while the two are falling to the ground after being attacked on the plane by Lord Loss, and Grubbs proves him right by flying to ground with Beranabus.
He has shown great cunning, emphasized in his chess match with Lord Loss. When he realizes that the demon master is feeding off his disappointment in losing pieces, he puts on a bored,uninterested facade and defeats him. Although he wasn't as good at chess as Lord Loss, he confused the demon which caused him to make mistakes.
He also has the power to fight off his own wolfen gene, which no other Grady has done before, and is able to retain at least a certain degree of awareness when he turns into a wolf.
Due to this potentially immense power, it is confirmed in Demon Apocalypse that, like Kernel Fleck, Grubbs is part of the Kah-Gash when, in that book, he, Kernel and Bec link hands and travel back in time, which is also supposed to be impossible, even to masters of magic like Beranabus, Bartholomew Garadex and Lord Loss.
He also has the power to change his form freely from human to werewolf and even a mixture of both, as seen in Wolf Island. In this novel, he changes into a werewolf to save the group from being eaten but changes part of himself to human again so that he can communicate with the humans of the group. Grubbs states, however, that he prefers being part werewolf/part human to being fully human. This is because he can be with his family (Grady's who have been affected with lycanthropy) and his human friends, and communicate with both, also he admits that when he is part werewolf/part human he feels complete for the first time.