Rakhshi Power-Up: What is their power-up? Are they exposed to a hazardous material, or imbued with energy by Makuta? Are they so strong that they can wipe the floor with the Toa, in their current states? There should be a sense of progression for the Toa, facing insurmountable odds and pushing through, so Sidorak might work (although we have to establish what he is, exactly).
Toa: Do the Toa get a power-up in Year 3? If so, I have a pitch here that could help you figure that out. If not, no worries.
Ekimu’s Chamber: What’s the layout? How many passageways (I was thinking 6, 1 for each Toa to venture alone through)?