Horuku (ホルク), first introduced in the new Monster Hunter Frontier Season Forward 2, is a Flying Wyvern type creature that is able to help the Hunter in battle. They are customizable, and can be equipped with skills such as shooting elemental balls/beams, healing/buffing players and placing bombs. They will also physically attack monsters by swooping down on them and clawing them with their talons.
Informally known as Halk, their elemental nature (as well as their appearance) can be changed by feeding them. Halks can use one element and one ailment simultaneously. The elements they can utilise are Fire, Water, Thunder, Ice or Dragon and the ailments are Poison, Paralysis or Sleep.
As of Monster Hunter Frontier Forward 4, Halks can now "carry" hunters in the same fashion as a Farcaster. The Halk will transport the Hunter to any area in the map at random when the hunter uses a special item that can be dropped in sets of 30 by the Halks post-quest clear or through GDP combination at the elder combiner in Mezaporta Square.
From the top left corner to the bottom right corner: Thunder Halk, Basic Halk, Fire Halk, Ice Halk, Dragon Halk and Water Halk.