Umbra

Umbra was a giant warrior who lived on Voya Nui: guarding the Ignika, Mask of Life from those who would misuse it. He was appointed as a guardian of the mask by the Order of Mata Nui, though he is not a member of the Order.

Anyone who wished to claim the Mask would have to defeat him in battle first, even Order members. However, he had been secluded near the mask for a long time, so he might not have even be aware of what happensed on the island's surface (including the fact that the Order sent Axonn and Brutaka to Voya Nui).

Umbra is actually not his real name, but one given to him by the Order so that he could fit in with enemies and gain their trust.

Umbra's exact powers are unknown, but they were based in the element of light. Umbra wielded a large, double-bladed staff that could fire lasers: it's also equipped with a Rhotuka launcher that can create hard light projectiles. He wore a Great Ruru shaped Kanohi mask, but the mask was powerless. He also had ultra-speed skates on his feet that allowed him to move as if at the speed of light. They also allowed him to ride on walls and ceilings, a major tactical advantage considering he was constantly underground.

Trivia
Umbra used to serve the Hand of Artakha, though he wasn't a member.