It is amazing how complicated the Oryx fight is, and how many individual mechanics it has. As an exercise, I tried to see if I could explain all the mechanics of the Raid boss fights in one sentence. Here we go.
Atheon teleports half the Guardians to the past/future to have Oracles kill them, but Kabr's relic allows them to fight back against the Oracles and eventually Atheon, while the team that stays in the present is Detained but can escape to open a Portal to past/present and allow them to rejoin their fireteam and make their own fate.
Mechanics: Oracles, Cleansing, Detain Shields, Portals, Sync Plates, Relics.
Crota taunts the Guardians to challenge him directly since he can only be killed by the Sword Logic, and so the Guardians must steal a Sword and stagger him to allow the Swordbearer to damage him, which is difficult since all the while, Crota's physical presence in his Throne World prevents healing and the Oversoul ensures any guardian deaths are shared by the whole team.
Mechanics: Swordbearing, Lack of healing, Oversoul
Skolas may be back in Prison, but he can still be challenged and finally killed by Guardians who defeat his Servitors that allow him to heal and can juggle a poisonous Taint, and all while Variks occasionally questions why he allows this at all and puts out mines that must be dismantled to blow everyone up.
Mechanics: Servitor Bonds, Taint, Dismantle Mines
Oryx likes to smash his fists on platforms to create a tear between dimensions that the Guardians can enter to chase an interdimensional brand that is above the arena on a series of platforms that are called into existence by guardians standing on the platforms, which once grabbed allows the runner Guardian to steal a brand of immortality from a Vessel of Oryx Knight that is guarded by a Hive Ship that will allow the guardians to survive detonations of Darkness Blights which are leftover from Light Eater Ogres that are summoned when Oryx smashes his fist, but must also be protected from Knights that eat Dark Blights and/or the Vessel of Oryx, because when Oryx's chest opens up to expose his vulnerability when he tries to kill the guardians with the same Darkness Blights but if the Guardians stagger Oryx he instead can be damaged by the blights of concentrated Darkness and once that's done the Guardians must either run away from Darkness Blasts or kill one of Oryx's shades in a Shadow Realm, which must be defended from the outside from enemies rushing in, which having completed all of this will allow the Guardians to kill Oryx during his last stand.
Whew. Worst run-on sentence ever.
Mechanics: Interdimensional running, platforming (jumping), platforming (plate holding), brand stealing, orb detonation, echo fighting, blight blasts that must be escaped, staggering Oryx's chest
I like Atheon's the most. It's cohesive, both mechanically and lore-wise.
The Oryx fight didn't feel cohesive to me like the other ones, but on reflection, it does use just about every mechanic from the Taken King. The only new to Raid Oryx mechanic is orb detonation. The rest of the mechanics are from all over Taken King. Being "taken" is obvious, platforming on hidden plates happens all over the Dreadnaught, brands are used throughout the raid, blight blasts are used by his Echoes, fighting echoes is throughout the story.
It's basically every trick Oryx has and has ever used. Which is really cool. I just wish they knit together a bit better for that final encounter like the other Raid bosses.
The one thing I don't like as much is that every Brand does something different. This one gives you Deathsinger Power, this one kills you if you don't kill stuff, this one makes you Unravelable/ Immortal.