Talk:Episodes, films, and shorts/@comment-21244319-20150211212504/@comment-26973802-20150212032245

And G1 Tirek was dead. (Although as Tartarus is hell that was initially thought by some to be how he got there, and is my theory on the Mane 6 sending him there, except that Celestia made it clear she and Luna sent him there after the Scorpan thing, while in G1 Tirek was killed by Megan with the Rainbow of Light during the Midnight Castle battle)

G1 and G4 are separate continuities. In G1, Tirek used the Rainbow of Darkness to turn ponies into demonic dragons. In G4, he eats ponies' magic. In G1, Tirek's top half is a demon, while in G4, his top half is a minotaur. In G1, Tirek turned a prince into Scorpan after taking over his kingdom, and Scorpan turned on him when he threatened to behead Spike. In G4, Scorpan was Tirek's brother who betrayed him out of friendship with the ponies, especially Starswirl the Bearded. In G1, Spike was with Scorpan from the start, while in G4, he was hatched from an egg by Twilight shortly before she got her cutie mark.

That being said, if they are willing to go with another villain, Grogar isn't that unlikely.