Eliminations II

"Hiding Place."

The tentacle centaurs...
...breathe hydrogen, therefore would not use copper oxide rectifiers exposed to their atmosphere.
- copied from here.

The Eksers generate electricity with copper oxide rectifiers exposed to the air.

The tentacle centaurs breathe hydrogen.

Strong electricity would raise the temperature.

At a slightly raised temperature, copper oxide and hydrogen would be transformed into hydrogen oxide (water) and copper.

Therefore, the rectifiers would cease to exist.

Therefore, hydrogen-breathers, like the tentacle centaurs, cannot be the Eksers.

This is one of the clues. However, some of us (me) do not know enough science.

Tomorrow, probably: "Margin of Profit."