Ring of the Dead and Guise of the deceiver
 

Probably stupid question but can a non DE shadowknight with dark elf illusion on equip ring of the dead?

No, illusions don't let you wear race restricted items

In theory for a very short time a non DE SK w/ Guise who has done additional faction work with The Dead to Warmly could MQ recharge the ring by handing in 10 gold after a zero charge ring hand in. Non DE cannot use it themselves, but could then give a recharged ring to another Level 1 DE as long as it remains tradable.