In the HOH:MC box page 32 it says at the end of the 4 samples of Elements (Ig,Aq,Au, Te): "Other elements should be based upon the effects listed here."
What are those "other elements"?
I understand that it refers to what is explained in the text, of the middle column, that is: "This body may be made of one of the traditional four elements of earth, fi re, air, or water, or other matter such as smoke or shadow."
Do you have any other ideas apart smoke and shadow?
I already decided that ice is an Aquam thing as per the rules, Lava or magma for Ig(AqTe) combinations, but I'm having troubles seeing other examples.
The mystery of the Anima allows you to turn into a "Spiritual or elemental form", so theoretically you could be entirely spiritual and be immaterial like a ghost - this would be like having the power "incorporeal form" from RoP:M p94 on permanently.
As for elemental form - if you're using "Other matter", then let's see what Art & Academe says. The bit on alchemical reagents on A&A p74 says Alchemists recognise simple matter (the vast majority is the same type of particle - air/earth/ fire/ water) and complex matter - complex matter types mentioned are "glass, metal, wood, smoke, clouds, oil, vinegar, lightning, and so forth" - so having a body made out of any of these would be acceptable. I wouldn't recommend a glass heartbeast if you plan to adventure.