This build for [Grendel] revolves around making use of his new augment, [Gourmand] (not currently in the Overframe Builder, just imagine it's present in the build), which allows him to utilize his large health pool to swallow enemies in place of energy, and Gloom, which allows [Grendel] to simply be dealing damange from either his weapons or his abilities to replenish his health. This build is really good and really fun IMO because unlike in the past where you would have to put an extreme ammount of effort to keep his energy up, you can simply manage your energy for the sake of casting Nourish and go on safely dealing damage with either Pulverize or with Weapons, even at the max cap of 40 enemies eaten since Gloom will be able to easily offset the nasty health drain.

Certain YouTubers have made the claim that Gloom's Lifesteal does not work with this new Feast augment, and simply put this is not true. As mentioned before you'll still be healing with either Ability or Weapon damage, just make sure you cast Gloom first before you cast anything else to make sure it's active. I went ahead and recorded some footage as proof.

Full Umbral mod set + [Adaptation] is to take advantage of [Grendel]'s inherent tankiness and also to get a lot of power strength with just 3 mods (301% if Growing Power is active.) I experimented with both +Efficiency and -Duration builds and +Duration and -Efficiency builds, and in my opinion the latter is more managable because you don't have to be constantly recasting your Nourish buffs. [Cunning Drift] is preferred since it's just nice to have a small ammount of extra range on all of his abiliites, but you can also use [Power Drift] if you want as much strength as possible. You'll be taking extra damage from the Health Drain, but Gloom is so powerful with as much power strength as this build has that it doesn't really matter as long as you're constantly fighting. You still do want [Streamline] in the build so you can cast all 3 buffs however. Arcane Energize helps make the energy usage more bearable, and [Guardian] just helps you get more Armor which [Grendel] likes. Grace can be run over [Guardian] but it's kind of redundant on this build and not really noticable. Lastly Gloom is subsumed over Regurgitate due to it being kind of useless compared to everything else.