The Oryx fight will be very different from previous bosses in that the player cannot do any damage to Oryx at all.
Oryx can only be damaged by Darkness. Darkness that all the other enemies (read: Taken) will be firing at us.
The only way to damage Oryx is to basically "cleanse" a group of adds, who will then turn to fire at Oryx for a brief period of time. Guardians will have a relic that will cleanse a group of enemies with a very long cool down. So you'll want to find a good sized enemy group to cleanse. You don't want to cleanse like a single dreg and a vandal. You'll only do like 3% damage to Oryx. You want to cleanse like a group of 6 or 7 enemies to drop his health by like 10-18%.
This is how Bungie is getting around the G'horn spam, by not even letting the players damage the boss themselves. Instead the whole fight will be about avoidance and add cleanup. Because once you cleanse a group of enemies, you obviously want to keep them alive as long as possible from other adds.
Eventually Oryx will make his way over and destroy them no matter what, but that's the difference between the 10% and 18%.
Relics will be lost on use, and you'll have to traverse the map to find another one to use. They'll spawn like the new Spark does in the Rift mode except in various spots. Similar to the spark, if you don't use it within X time, you'll die from self combustion.
Also bored at work.
Obviously none of this is true. I'm just making it up as I go.
It....sounds all true.
You know they'll make use of that spark thing in the raid at least.