Viral mods proc viral status which boost damage to health by up to 4.25x.
[Accelerated Isotope] adds radiation status and fire rate.
[Anemic Agility] and [Lethal Torrent] add further fire rate to help charge alt fire.
Augur mods like [Augur Seeker] and [Augur Pact] help with shield gating.
[Amalgam Barrel Diffusion] gives multishot for priming and helps you roll faster. Flexible for [Augur Pact].

Exilus Mod is flexible based on your setup requirements. Note these will be activated by ABILITY kills, as long as they have recently been damaged by Grimoire (either primary or alt-fire):

• Khra Canticle - gives even more energy economy
• Jahu Canticle - gives free 5% armor strip per kill in affinity range which is 50metres. This can really add up for boosting DPS, as after 20 kills you can full strip enemies 50 m away.
• Lohk Canticle - free fire rate

Invocation mod is also flexible based on your requirements. The default mod to run is Xata invocation since it gives a huge amount of energy regen.

• Xata Invocation - gives up to 10 energy per second for 20s, for a total of 200 energy per alt-fire.
• Netra Invocation - free ability efficiency of up to 60% for 20s, but does not snapshot on channeling abilities
• Vome Invocation - free ability strength up to 60% for 20s, and does snapshot on channeling abilities
• Ris Invocation - free ability duration up to 60% for 20s, does not snapshot on channeling abiliities

Arcane is flexible based on needs:

• Secondary Encumber - allows you to proc all unique status effects up to 13 to boost condition overload type mods
• Secondary Dexterity - for melee focused builds
• Conjunction Voltage - gives extra multishot for priming viral