This shit melts lol
Before you go to get ur Sister of Parvos make sure to use the right warframe to obtain the element that you want, in this case i went for Toxin. (But i think you can also can go for magnetic)
Things to consider:
In case you have or want a riven for this weapon, try looking for something with CritChance/CritDamage/MultiShot/Damage and for the curse -Zoom, -Puncture/Impact.
The riven can replace Lethal Torrent
This build can work with just 2 forma but i recommend to you investing 5 forma since the level of all Tenet weapon caps on 40 depending the amount of Formas used.
If you want to use an Exilus Mod i would recommend Ruinous Extension.
The Tenet Cyrcron has a passive that when hitting a enemy it can [Extend] that damage to nearby enemies which is kinda an AOE.