Discorded Sirius Veil, both as a foal and an adult.
 
So, you remember how I once mentioned that Discord used to mentor Sirius is magic? Yeah, it was because the colt was veyr proficient in chaos based magic. So much so, folks wondered if Sirius was really Twilight’s son at all. He is but his proficiency in Chaos based magic is due to Twilight’s unique experience in becoming Discorded back in Return of Harmony. Unlike her friends who were tricked or forced to become their worst selves, Twilight discorded herself when she gave up on her friends and on winning. When she ‘cured’ herself, the discord magic within her remained.
 
Anyway, Sirius is very good at this kind of magic but doesn’t use it unless he is upset or mad, mostly because it tends to do a lot more harm than good. He is the prince of Friendship! He has to set a good example. But there are days when his envious heart gets the better of him and he gets just a bit discorded. He’s only gotten fully Discorded once but quickly forgot about it later. He doesn’t remember what he’d done those few hours but after that, Discord was not allowed to teach him any more chaotic spells
 
Note: Discorded Sirius is a lot more dangerous than almost anyone. He is as random as Discord but collected like his mothers. He gets these weird twitches that lead to him doing something either strange or crazy. He’s kinda of like a dark knight joker except mixed with a sugar rush. He’s very very twitchy when he’s like this… I don’t know how to explain it. Another thing is that his mane sparkles when he uses magic.
 
Despite being a nice guy, Sirius is a very jealous pony. He envies his cousins wings, he envies his brothers magic, he envies his fellow foals ability to make friends and he envies his mother for the love she receives from others despite her faults. This leads to a lot of problems for Sirius since he tends to bottle up his problems until they explode. He’s only discorded a few times but each time ended up causing a lot of damage and leading to Twilight taking her son to visit the Everfree forest. No one knows what she does there but every time she comes back, all that was done is forgotten by everyone in town.