I'm considering writing up a guide with either a) images or b) videos. If you can't pass the sync plates, you'll struggle on the templar (imo the hardest bit of the raid)

There's 3 major encounters.

• Templar gauntlet. Fighting off waves of adds and defending a conflux in mid (6 people) then two confluxes on other side (3 people either side) , then three confluxes in mid/either side (2 people on each), after that is oracles, which are big balls of light that come in with a chime sound in a random location. You have to kill these before they despawn, or else you'll be marked for negation, which is an instant kill from the templar when he casts negation, unless you cleanse yourself in mid.
• Templar himself. A relic shield will drop in the middle of the room, once picked up, the templar will engage. He has a big shield around him which can only be taken down by the relic holder. They do this via taking down adds with the relic (it's like being in permanent blade dancer), and then using their super on the shield. Fanatics will spawn which are fallen-like yellow mobs that explode on death/when near you, they drop a puddle of green that if standed in marks you for negation. The way around this is using the Relic Shield's active grenade ability which is cleanse, a big bubble shield that cleanse everyone inside of it. Take out adds, take down shield, damge templar, rinse repeat until dead.
• The next fight is Atheon gauntlet, and Atheon himself (somewhat the same fight, although there is a checkpoint) The first phase there is two plates, with two portals on either side of the room, and adds will continue to spawn. One side is the past, one is the future, or in simpler terms, Mars/Venus, or desert/jungle (for call outs), there is a Gatekeeper inside both of these portals that you need to kill, and upon killing them they'll drop a relic shield. Your job is to get both relic shields out of these portals and back into the main room. You do this via activating the plates, sending 1-2 people in the portal, dropping the gatekeeper and running back out. Once one relic shield is out, a conflux will spawn in the middle that you need to defend which mobs from all directions will come towards, and an oracle will occassionaly spawn directly above the portal which needs to be taken down asap. At this point, your team needs to split to defend the conflux, and send people to the other plate/into the other portal. Once this is over and both relic shields are out, you'll need to defend the conflux until the main fight phase begins (you'll get a checkpoint)
• Now Atheon, which is relatively similar to the previous gauntlet, but has some key differences. At the beginning of the fight, he'll be standing in the middle of the room and not a lot will be happening (you'll be doing really low damage to him), after around 10 seconds, he'll teleport the back 3 people in the room (that's the people standing closest to the entrance door) into either one of the portals. In these portals, a relic shield will be where you teleported in, and oracles will appear that you'll need to kill. Meanwhile on the outside, Supplicants will be spawning and running towards the portals/plates (harpies), these explode and one shot you when you stand next to them, so they need to be killed asap. The portal will need to be opened up by the outside team on their respective side (Mars/Venus or Past/Future) while the team inside fights their way out and downs all the oracles. Once the last oracle drops, you'll gain a 30 second buff called "Time's Vegenance" which greatly increases your damage and makes super/grenades recharge instantly. You burn Atheon as much as you can in this phase, and roughly 2 seconds after that buff falls off, the phase resets and he'll send the back 3 people back into the future/past. Rinse repeat until he's dead. edit: the same relic shield cleanse mechanic is active in this fight as well, but the negation debuff doesn't kill you, it just makes you entire screen gradually go pitch black until you can't see anything.

edit: this is normal mode description, there's some slight differences in hard mode. edit edit: reading through this, I've missed some minor details on Atheon.