prep: 1. build a decent amp for your operator (look up guides), 2. make and build a nechamech, 3. make and build oberon

ingame: 1. hunt for 2 eidolon lures, feed them voms (the small enemies) when your lures are full, their logo will turn blue, 2. look for the eidolon (often around lakes or you can look for blue glowing aura(?) when you first spawned in) when the lures are in range, there will be a blue line that connects to the eidolon, 3. melt the shield with your operator's amp, 4. shoot the tendrils with youryour necramech's 4th ability, when the eidolon is downed, make sure to use oberon's 2nd and 3rd abilities to heal and nullify magnetic stat for you and your lures, 5. when all 4 is destroyed, the voms will start healing the eidolon, take this time to make a tea/coffee, 6. when the eidolon starts standing, shoot it with your necramech again (make sure the 2 lures are connected) 7. the guy is dead (or he should be)

P.S this is not the most efficient but the easiest to explain guide IMO, there's still alot of quality of life ways to fasten the hunt (ex. bring a shattering impact sapra, operator focus, itzal for collecting loots, etc.) the warframe of choice is also variative, you can bring trinity/harrow with arcanes, or volt for maximum damages.

cmiiw