ettmetal

[taveren he/him]

so is the metal they used to run their machines just lithium

[+Lewis Nethur He/Him]

Assuming the metal isn't an alloy and belongs to our known periodic table of elements, and considering the violence of the reaction they described when contacting water and the mass of ettmetal they loosely implied was available...and without getting bogged down in too much math and chemistry, I would be more inclined to assume that the so-called "ettmetal" was equivalent to one of our 4th or 5th row alkali or alkali earth metals (IE: Potassium, Calcium, Rubidium, or Strontium), as opposed to lithium.

 

However, based on the information provided, I think you're probably in the right ballpark and narrowing it down further at this point would be fairly difficult and imprecise.

[taveren he/him]

just a guess since they are essentially using it as a battery and it burns in water

[Weltall]

Potassium was my first thought, assuming it's something we actually have an analogue for. Hmmm, maybe Aradel's banana in Shadows of Self was foreshadowing.