AD&D Psionics Elemental Composition Help

Rules AD&D 2nd Edition
#1

Hey everybody. So I am currently playing in an AD&D game as an 11th level psionicist who just learned the High Science Elemental Composition (Power description on page 74 of The Will and The Way) but I’m having trouble understanding it.

First of all, what constitutes an element? The description lists; iron, obsidian, sand, earth, water, air, stone, and even nitrogen gas. Does this mean anything on the periodic table? Are compounds acceptable as well, ie water, air, etc? I even tried looking up elemental creatures but all I could find are the four basic elementals which leads to my next question.

If I roll powerscore I “gain the combat ability of an elemental of the appropriate type,” but I can only find descriptions of the four basic elementals. Does that mean I pick the one of the four that most closely relates to my element? What if I change elements as the power allows, do I keep that original ability or does it change to my current elements ability or even just lose the ability all together?

My DM says he will honor any guidelines I can cite so if there is anything that can help from the Dark Sun lexicon please tell me as he prefers to only use homebrew rules when there is no other option.

#2

Reading through the description it seems to use both the classic elements (Air, Earth, Water, but not fire), as well as various forms of each. It explcitly notes that the Power Score gives you the combat abilities of such an elemental.

From this I (personally) would allow any non damaging naturally occurring material to be used as the form assumed - you can become like Iron, but not like Steel (an alloy). You can become a cloud of oxygen, nitrogen or plain air (a mostly nitrogen/oxygen mix), but chlorine gas. Fire also seems to be the big exception to the listed forms - probably because fire burns. Extrapolating that to the periodic table, I’d say Uranium-238 would be permissible as a choice, but Plutonium wouldn’t (U-238 is radioactive, but not generally lethally so except if ingested in massive quantities, PU is highly radioactive in its natural state).

Anything you can find in nature that doesn’t automatically do damage would be the safe (and short way) of summing things up for Elemental Composition.