Mineru

The Spirit Temple asks you to attach parts to a frame. Arms can hold a weapon or a zonai device such as a cannon, a flame emitter or a shock emitter. Wheels and fans change how she moves, and they drink the cell faster. A simple body with a strong horn on the arm is easier to live with than a cannon that empties the battery in one room. You can rebuild her later when you have more devices.

The temple boss is a seized construct, and you fight it like a Flux Construct: find the glowing core and hit that, not the outer blocks. Mineru's body can stand in front and take the first hits. Ultrahand still pulls a loose core. When the core breaks, the temple is done and the vow is yours. Do not go in with an empty battery. Her body is the weapon, and a dead cell makes her a statue.

Summon her in the field and you can climb onto her back. She walks through gloom that would paint your hearts if you waded in on foot, and her swings use whatever you attached. A horn arm is a slow, heavy hit. An emitter arm is a beam that keeps spending energy. She is wide. Do not summon her on a narrow sky bridge or she will walk both of you off it.

She is the sage for the Depths, the way Tulin is the sage for the sky. Bring her to Frox basins and to the roads under the castle when you want something else to take the hit. Dismiss her when you need to Ascend through a small hole or sneak a chest. The battery she spends is the same cell your fan bike uses, so a long ride on Mineru is a reason to stop at the next forge.