Little "easter eggs" like that are pretty rad! I seem to remember there was a story behind the knife (from the Q&A) but I don't think anything concrete was revealed.
SEKAI2 votesI think the blade on Sion's head is just a random knife token from the war times that has Jarvan the First's blood on it.
Similar to how he now has J1's crown as his new jaw, those 2 objects are only there to awaken Sion's memories and consciousness in his long dead body during the resurrection ritual and not much else.
So I wouldn't say there is a link between SotO and Sion's "ponytail".
Solideus1 votesOh I never said there is a connection now, I just think it would've been a nice new icon/"story" for the item. I somehow forgot it was named SWORD if the Occult though; maybe the Void, SI or somewhere else would be a better theme for it.
Shíny1 votesI fully support this. 
kagepaladin2 voteshow many supports would you throw at riot to "support" this. 
.... wow just realised how many potential supports their are in game. :O
AbodyHUN6661 votes
Don't forget the cheese supports too.
Boogs1 votesForgot 
:[3
manliestdino1 votesIf you want cheese supports you get
and yes I have played with or against all of these supports (except maybe gnar)
ElJanitorFrank1 votesSion has a bunch of easter eggs already. Give him more we might as well give him an easter skin.
Just a few examples: His jaw is Jarvan I's crown, his shoulderplate is Full Metal Rammus' shell.
Spacesuit Spiff1 votesI always assumed it was J3's flag thingy
Helmight1 votesYou've got my vote. That'd be a pretty cool easter egg, same as the Seeker's Armguard belonging to Sejuani
67450548_DEL1 votes[deleted]
Solideus2 votesThat's really cool! I'd love a little more alternate-canon stuff to be played with.
