The "secret" 60 Eyes boss is spawned on the new Assassination node on Deimos - Effervo. The mission only requires you to gather 30 Eyes, however if you continue collecting up to 60 Eyes, you will spawn the super boss rather than its regular variant. It's very tanky with pretty devastating special attacks that keep you on your toes as it is imperative that you avoid them - they cannot be face-tanked.
I find this an immensely fun boss fight, to the degree that I don't want to give too much unsolicited advice because I think it's great if people experience it and figure it out for themselves. However if anyone would like some general pointers to help them prepare before tackling it, I have some below:
The first most threatening part of the fight is catching Magnetic procs - This mostly occurs when the boss performs a frontal melee slam with a wide area of effect, but the snake Murmur ads are a frequent source as well. If you go into the fight assuming that you will not dodge perfectly and it is inevitable that some these attacks will catch you, you can prepare and build around preventing/recovering from it - Arcane Nullifier will prevent Magnetic procs and preserve your energy, and Rolling Guard is a quick status cleanse plus 3 seconds of invulnerability to reposition and recover. The Wyrm companion also has its Negate precept to prevent status effects
The second most threatening part of the fight is having your abilities dispelled and being unable to cast for a few seconds - This occurs when the boss's spinning laser attack hits you. Typically the first laser will hit you with the nullifier effect, then the second will swing around and one-shot your vulnerable health while you are unable to cast. Rolling Guard is a very effective panic/invulnerability button to protect yourself and recover from a laser hit. If you assume that getting hit at some point is inevitable, then you can prepare for frequent and inevitable re-casts of your defensive and offensive abilities and allow for a good energy economy
The first phase of the fight has very few ads - just a random Eximus every now and then - This means the first phase is where you are most likely to run out of energy and/or ammo. Incarnon weapons with their free ammo from their Incarnon forms, or battery weapons that cannot run out of ammo, can prevent this being a problem. Energy can be managed by not catching constant Magnetic procs and not building deeply into negative efficiency
The second phase of the fight has far more ads - This is good, because if you have effective area clearing you are provided with far more energy orbs, ammo, and Arcane/Galvanized stacks. However, this is also bad, because it can make the fight very chaotic and distract you from watching the boss and dodging its special attacks
There are no self revives, like in Archon hunts - Prioritise reviving your teammates. If you go down yourself, you can go into Last Gasp to prolong your bleedout timer even if you don't think you have a chance at pulling off a self-revive, but make sure to put a waypoint on your downed Warframe to help your teammates find it in the clusterfuck chaos
Stay mobile and stay focused - Once you have a feel for the fight and the boss's attacks, the biggest deciding factor is your own consistency in not getting caught out and not going down. Move lots, dodge everything you can, and try not to tunnel vision on ads and take your eyes off the boss for too long. Remember that the boss is always the main focus and the ads are just a distraction