Knack is a creation of The Doctor, and was created from ancient relics. His purpose is essentially to aid humanity in the war against the Gundahar led Goblins. He is able to transform himself into both large and small forms through the use of ancient relics dependent on the situation and action warranted. While in his smaller form, Knack is able to more effectively traverse small, restricted areas, crawling through ducts, tunnels, and cracks in order to progress. In his larger form, Knack is more formidable than before, able to move large objects, deal with larger enemies, and perform melee combos.
Knack is able to transform into various materials and sizes, and use these transformations both for exploration and combat.
Ice Knack is the elemental transformation of Knack in which he is clad in ice. While this offers significantly more protection than his normal form, he is prone to damage via melting.
In this form, Knack is clad in metal, which makes him both a juggernaut in terms of defense and a force to be reckoned with in terms of offense. This has a trade-off, however, in that Knack is turned magnetic when he is in this form, leading to some interesting weaknesses (and potential solutions to puzzles involving magnetism).
In this form, Knack is clad in wooden sheathes, but is susceptible to fire and prolonged damage from burning.
In stealth mode,Knack can go through lasers without being detected.