I know this thread has been dead for awhile, but I want to share a theory a friend of mine and myself have been discussing, and it's relatively close to what others have been saying here:
Discord and Celestia have been playing a long, drawn out game of chess, using ponies as pieces (or in Discord's case, magic and the environment). It's pretty plausible, considering what happens throughout the seasons. Celestia wanted Discord released, to continue the game they had been playing, as Celestia had finally found a pawn (Twilight) who has a chance of crossing the board and becoming a Queen (alicorn).
I don't believe Celestia is as powerful as she lets on; while she does seem to know some amount of advanced magic, it's very limited compared to Twilight or even Starswirl. She relies heavily on others to complete tasks, her only duties are ruling and raising the sun (and even the moon, in her sister's absence). While these are no small feats, it's what's within her talent, so it shows even alicorns are limited by cutie marks. So she may not have been able to defend herself against these particular vines, not that she even really wanted to.
This is by far my favorite episode, mainly because it made a little roleplay group I run canon, more or less. I was squeeing so hardcore during the entirety of that. About fainted when I saw Nimmy. <3
I know this thread has been dead for awhile, but I want to share a theory a friend of mine and myself have been discussing, and it's relatively close to what others have been saying here: Discord and Celestia have been playing a long, drawn out game of chess, using ponies as pieces (or in Discord's case, magic and the environment). It's pretty plausible, considering what happens throughout the seasons. Celestia wanted Discord released, to continue the game they had been playing, as Celestia had finally found a pawn (Twilight) who has a chance of crossing the board and becoming a Queen (alicorn). I don't believe Celestia is as powerful as she lets on; while she does seem to know some amount of advanced magic, it's very limited compared to Twilight or even Starswirl. She relies heavily on others to complete tasks, her only duties are ruling and raising the sun (and even the moon, in her sister's absence). While these are no small feats, it's what's within her talent, so it shows even alicorns are limited by cutie marks. So she may not have been able to defend herself against these particular vines, not that she even really wanted to.