Considering all the recent heated conversation about Venser, Karn, and sparks, I think I've thought of some interesting exceptions thanks to Theros. According to the lore, if a sentient living creature dies, it definitely enters the underworld one or another. Infrequently, some will struggle and escape the underworld, but not as they were before. Their body and soul split, releasing a Noston (Returned) and an Eidolon into Theros. CAN this mean that the Eidolon formed when a Planeswalker dies and escaped the underworld be a living embodiment of the Planeswalker's Spark? Even more interesting that eidolons are AURA Enchantment Creatures. Also, because it is explained that one's body and soul both reach the Underworld together, and the deceased have the risk of becoming so embittered by their time in the Underworld that these individuals become demons... does that not mean that the possibility that a Planeswalker can become a demon like Ob Nixilis w/o losing touch with his spark?
Removed your illegal solicitation