This is a build for [Nekros] that uses Blood Altar.
Blood Altar is the helminth subsumable [Garuda] skill.

Not only does it heal you, it also heals companions, other players and objectives (excluding defense mission objectives).
Most importantly, it heals your SHADOWS. That is why range is prioritized and duration is foregone.

Three regular formas are required for this build.

Combos

1. Blood Altar -> Roll (Dodge) -> Shadows of the Dead (total energy cost: 232.5) (shield conversion: 348.75)

2. Blood Altar -> Terrify -> Roll (Dodge) -> Shadows of the Dead (total energy cost: 348.75) (shield conversion: 523.125)

3. Blood Altar -> Terrify -> Roll (Dodge) -> Shadows of the Dead -> Blood Altar x2 (total energy cost: 503.75) (shield conversion: 755.625)

Notes:
-Rolling Guard provides invulnerability during the cast animation of Shadows of the Dead (which is dreadfully long, ~4 seconds)
-Invulnerability will wear off before the cast animation of Shadows of the Dead is finished, but the Shadows will take aggro as soon as they're spawned
-Use Amalgam Barrel Diffusion to maximize the benefits of Rolling Guard (it's significant - try it)
-Healing and shield conversion BOTH ACTIVATE NORMALLY WHEN INVULNERABLE
-Shield conversion above maximum shield capacity (450) does not turn into overshields due to Brief Respite's limitation

Core Mods

Shield of Shadows - maximum damage reduction is 90%, of which 89.88% can be achieved at 214% ability strength

Despoil - whether it be farming or tanking Nekros build, this mod is a must

Brief Respite - provides shield instantly, which is valuable in high level missions due to shield gating

Blind Rage & Power Drift - 214% ability strength, nuff said; Blind Rage's negative ability efficiency synergizes with Brief Respite

Stretch - the pitiful heal range of Blood Altar is improved; all of Nekros' kit is affected by range

Equilibrium - have companions equip Synth Fiber to pick up health orbs even at full health; Desecrate drops a lot of health orbs

(Primed) Flow - allows the use of other abilities after using Shadows of the Dead
([Nekros Prime] max energy at lv 30: 188) (Shadows of the Dead energy cost with Blind Rage: 155)

Arcane Suggestions

In General - in this build, arcane choices are highly flexible; Arcane Energize and Guardian are just suggestions

Arcane Energize - in the highest level missions (eg. Steel Path) enemies don't die fast enough for constant energy gain (especially effective with Energy Generator Dethcube)

Arcane Guardian - replaces [Health Conversion], opening up a mod slot while maintaining the tankiness

Weapon Suggestions

In General - Nekros Desecrate benefits from Slash and Cold damage types, since they cut/shatter corpses into multiple pieces which all get Desecrated separately

Primary - No suggestion

Secondary -
Pyrana Prime/Amalgam Barrel Diffusion increases the value of Rolling Guard

Melee -
Hate/It's thematic

Companion -
Non-Sentinels/Link Armor works with Arcane [Guardian] and Health Conversion

Substitutions

Stretch - Augur Reach, -15% ability range for broader options for the aura mod

Rolling Guard - Health Conversion or Adaptation

Vitality - Umbral Vitality

Stretch, Vitality - Umbral Intensify, Umbral Vitality (requires Umbra forma, -45% ability range, +55% ability power, +110 health)

Power Drift, Stretch, Vitality - Cunning Drift, Umbral Intensify, Umbral Vitality (requires Umbra forma, -30% ability range, +40% ability power, +110 health)

More Configs

Config A (Blood Altar, Umbra Forma)

Config B (Blood Altar, No Umbra Forma)

Config C (Petrify, Farm)

Thank you for reading!