For the real loot at the end you need 2 charged "eidolon lures" They get charged by letting the smaller sentients near the lure while they're in their blue form. 3 per lures, so a total of 6. You can also charge them by bringing the loot-beam drops from the smaller sentients to the lures (you'll glow when you touch them). You need at least 1 charged lure from the start for a smooth kill. Otherwise the eidolon will teleport away when you destroy a weak point.
For the actual fight you need to shoot him as an operator till his shield falls. Shooting through Volts shield is the only way to boost operator damage. Then you need to shoot him (with any gun), aim for his weakpoints on his knees or arms. Current meta is Vexing armour Chroma with a Lanka.
He has various abilities, watch out for them, learn them. Of note is the healing phases. In the shield healing phase, he draws energy from nearby smaller sentients. This can happen any time his shield is down after the second(?) weakpoint is destroyed. End this phase by destroying the physical body of all nearby smaller sentients, prevent it by killing all the smaller smaller sentients regularily. In the health healing phase, he calls for the smaller sentients, which will come from afar in their blue form. The more of these that get to him, the more health he will have in his final form. Kill them by shooting them as an operator.
Final form, starts out with no shields, but he can enter a shield healing phase at this point. He has no weakpoints but standard guns will hurt him if you hit any part of him. Make sure you have two charged lures, and shoot him till he dies.
Final notes: The lures can and do take damage from this fight. Make sure to use healing abilities like blessing or renewal to heal them, or Gara's (new frame) second ability to give them 90% damage reduction. (Watch a Gara solo video on youtube to understand how best to do this) The lures will follow who ever hacked them, in the mode they used to hack them. Hack them as a warframe? They'll follow your warframe. Hack them as an operator? They'll follow your operator. Use this to your advantage for positioning. The eidolon can spawn anywhere on the plains except the north-east and north-west hills, get those archwing charges made so you can search for him more easily. Mark him then find some lures to bring to him.
Oh. And the Eidolon is passive. It will not attack until it is attacked.
"Quick" run down of the fight. For the real loot at the end you need 2 charged "eidolon lures" They
Yeah, it's a lot to take in, but it's pretty linear. Not a lot of things going on at once. If you try the fight two or three times you should be able to get most of it down, the annoying part is keeping those lures alive.
Oh, I forgot. When you break a weak point (only the first three times, fourth one starts the health healing phase), he starts 'wailing'. And releases waves of magnetic energy that deal a combined totaly of over 17k damage. Best to switch to your operator and enter void mode (crouch) until it ends, or run out of it's range. Just make sure to leave the lures behind if you choose the second method.
Yeah, it's a lot to take in, but it's pretty linear. Not a lot of things going on at once. If you tr
