To be used with ### Rubico prime preferably as it kills very quickly (one shot in first round and 2/3 bullets on the next rounds always with headshots)

I use an Eidolon build for that, radiation is good in index against Corpus:
https://overframe.gg/build/220650/rubico-prime/eidolon-hunter/

You don't need to pick any energy orb the whole time if you use Zenurik school with maxed Energyzed Dash and stay in the rift under Cataclysm.

How to use

When the game start use Energyzed Dash immediatly then go to the rift by dashing (see [Limbo]'s passive) and wait until you have 105 energy (it's really quick) then cast cataclysm around your objective followed by Stasis. You can also get an energy orb if you want to speed the process.

Now you camp in the rift and kill everything who enter the Cataclysm (they will be frozen so easy headshots) and recast Stasis and Cataclysm as soon as they run out to keep the objective safe at all time.

At anytime use Energyzed Dash to replenish your energy quicker, typically after recasting your abilities. Tho it's not really needed with so much duration on the build.