I don't know, see, a Toxic True Element might not exist because Shadows of Asia mentions two corps battling over an area in the ocean where this new "radical" was found near an old Orichalcum deposit. One wants the radical and another wants oil resources (I believe) and so the theory is that the drilling of the oil would destroy the "nature" of the element.
However, one could speculate that if enough mana-lines were aspected towards a toxic nature, like the mana-line in Tsimshian, that toxic True elements might occur. However, I doubt many magicians would find a toxic True Element to be very useful.
[ED Alert]
Notably, a Horror in Earthdawn could Taint True elements and Orichalcum in order to sap karma from those whom bond to them (many of whom were blood-bonded via Life Magic artefacts) and also affect them with other Horror powers.
[/ED Alert]
Space still has "mana" in it, it simply has no charge. So Jester may have something with a hypothetical True Nothing. However, the scary part about this True Void, is that it smacks of the nature of the Enemy, to mindlessly consume anything with which it comes in contact. So a True Void and True Darkness would essentially be the same thing.
DnD had a magical item called a Sphere of Annihilation which would accurately mimick True Nothing.
