Here's another thing to consider - how do we know Tirek ISN'T dead? In Greek mythology Tartarus is another name for hell. The Mane 6 blasted Tirek, dark particles seemed to fly from him which could have been a disintegration, and he suddenly appears powerless in Tartarus (where he'd have ended up if he had died), with a cage around him, when Rainbow Power was unable to fix Twilight's library or the playground equipment, so how could it make a cage appear out of thin air?



Yes, he was alive the first time he was there and so were the princesses, but notice when he's shown imprisoned there, his cell is glowing, where the other two cells (one of which the princesses are in) weren't, maybe glowing cells denote damned souls, and, so as to not cheapen death as Dragonball Z does (where Frieza spends his afterlife imprisoned in a chrysalis in hell, but Goku could teleport into the afterlife while alive), maybe make them invisible to the living, on a different plane of Tartarus (like the concept of an astral plane). How do we know Sombra isn't spending his afterlife imprisoned in a cage in Tartarus too? (Chrysalis isn't, coz she's still alive)



But anyway, that's my theory, and I sometimes think it was meant to be ambiguous that way