These aren't just doubles--they are me. They are all me. Each one plucked from my past to aid me in the present. Instant army, ever loyal, and I can call on as many as I need. [...] Unfortunately, they--we--never seem to remember what we see in our own future.
The KanohiMohtrek was the Mask of Time Duplication. It gave its user the power to summon one or more past versions of themselves to the present. If any of the past selves were killed, the user would cease to exist, and an alternate timeline where the user died would be created. When the past versions were sent back to their time, their memories of the future were erased. However, any damage to their bodies remained. Bitil chose not to summon copies of himself prior to when he entered the Karda Nui swamp, fearing that they might be mutated also. The amount of concentration needed to keep the past selves in the present increased with the amount of selves summoned.