Gáe Bolg
From Inga no Kusari wiki
Gáe Bolg is Finn Green's fullbring.
At its third manifestation, the appearance of Gáe Bolg, both released and sealed, changes form. Gone is the simple spear head, it is replaced by a vicious looking shaped blade, stylised to represent the lightning that it is named after. The shaft also grows in length, now standing far taller than Finn himself. At the end, where there was once a blunt pommel, there is a vicious spike, perfect for gutting unfortunate enemies. It is constantly surrounded by crackling arcs of lightning, which come from both tips of the spear and dance over the body of it.
Fullbring Abilities
Gáe Bolg harnesses Finn's reiatsu to create a sort of 'spirit magnetism', in doing so, the blade, shaft, and Finn himself, have a tendency to repel ambient reiatsu and reishi. The only addition to this new level of power to Gáe Bolg is that the natural repulsion is stronger, and against weaker forms of reiatsu attack (such as a tier 1 or 2 cero, or similar), he is somewhat protected, the raw energy dampened to safer levels before hitting him.
When swung at something made from spirit particles, the spear can 'part' the particles, creating a path between them. This is not cutting. Solid objects develop a one or two foot gap in the wake of the spear's swing, and energy construct, such as a cero, tend to split into two parts, like a river flowing around a rock. Energy shields, after a while, will heal themselves, and beams have a tendency of only parting for a short distance before re-joining. The hole created in physical objects constructed from reishi, however, are permanent.
At this more advanced level, Gáe Bolg also becomes an effective offensive tool. The lightning crackling around the spear is formed from Finn's own reiatsu, and when it touches the flesh of a spiritually sensitive being, it burns just like a flame would. The lightning can be 'thrown' with a swing and some degree of concentration. Gathering around the spear's head, Finn can release the lightning in any way that he wishes. The high concentration of the reiatsu-lightning means that upon impact, a small explosion (man-sized) occurs.
Being that it is formed by the spear, the lightning generated by the spear possesses the same properties as the spear itself, only at a much smaller level. If the lightning were to hit anything, just as the spear, it would pass through it and leave a hole just large enough for the lightning itself.
In addition, if the spear is thrown from the 'fork' between Finn's toes (held between two toes, in other words), whilst he is stood in running water. Then Gáe Bolg will deliver a killing blow, no matter where the attack lands.
Strengths
Solid Defence - Most attacks in the world of spirits are made from some kind of spirit energy, and therefore, Finn can effectively defend himself from most attacks. He can't avoid harm from external threats such as falling masonry, or something made from something else spiritual, such as a zanpakutō, but in cases such as that, the fact it's a bladed weapon come into play.
Long Reach - Finn can wield Gáe Bolg from any length, even with his hands around very near to the end of the spear, meaning flying enemies, unless they're several stories above him, are easily attacked.
Repulsion Cushion - Now that Finn has come to understand his ability a little better, the unconsciously emitted field of repulsion serves to soften energy attacks directed towards him, making what would once deliver a burn or knock him down now merely bruise and nudge him out of his stance.
Ride the Lightning - Drawing out his own reiatsu, Finn can use the spear offensively against spiritual creatures without relying on having to be able to cut them. The damaged caused is burning, which, if done enough, could greatly hinder an enemy.
Weaknesses
Rock in a stream - The power of Gáe Bolg may defend Finn from harm, but as far as others are concerned, they can still be hurt. The splitting power does not destroy attacks that come his way, and for that reason, it's better for him to utilise the ability when fighting alone, than to risk those stood either side of (or behind) him getting hurt.
Pole Weapon - The shaft of Gáe Bolg is reinforced with spiritual energy, so it cannot be very easily cut in half, but even so, the bladed part of Finn's weapon takes up one seventh of the entire spear. The part that can deal damage more than bruising is small in comparison with the rest of the weapon. The lightning may burn opponents, but it is entirely random in its dancing across the shaft, it may well miss an opponent entirely.
Reach - Finn may be able to reach further than a melee combatant armed with a sword, but he still cannot hit birds high in the sky. He may be able to hit far off opponents, but a certain distance must be closed between them. The distance he must have with his enemy is short enough for the opponent to simply dash at him and make it a very close-quarters battle.
Does not play well with others - Due to the lightning that courses around the spear, and its unpredictable nature, Finn cannot fight closely with his allies, or he risks hurting them with a stray bolt. As such, he tends to be forced to work alone, which means he could very easily be outnumbered.
