Theorylytics

The Vast Untime

Used by Xaku

Ability4
Energy25

The Vast Untime

Temporarily shed the outer pieces of Xaku in a destructive blast, then stalk the battlefield in a new, swifter skeletal form. Enemies damaged by the body shrapnel are rendered weaker to Void Damage. Xaku's other active abilities' duration is frozen in time and resumes once The Vast Untime expires.

Introduced in Update 29.0 (2020-08-25)

Ability stats

Strength
  • See in-game / wiki ability card for rank values
Duration
  • See in-game / wiki ability card for rank values
Range
  • See in-game / wiki ability card for rank values
Misc
  • Temporarily shed the outer pieces of Xaku in a destructive blast, then stalk the battlefield in a new, swifter skeletal form.

Info

  • The Vast Untime is Xaku’s ability 4.
  • Temporarily shed the outer pieces of Xaku in a destructive blast, then stalk the battlefield in a new, swifter skeletal form.
  • Use it with the rest of the kit — especially Xata's Whisper, Grasp Of Lohk — instead of casting it in isolation.
  • Ability Strength, Duration, Range, and Efficiency each matter differently; check Mod Scaling below before dumping all four.

Augment

9

Untime Rift

The Vast Untime Augment: Creates a Rift that connects to enemies suffering from Void Status Effect within 15m, doubling debuffs applied b…

Xaku
Open augment →
Untime Rift

The Vast Untime Augment: Creates a Rift that connects to enemies suffering from Void Status Effect within 15m, doubling debuffs applied by The Vast Untime and maintaining Void Status.

Max rank drain ~9; see rank table on the augment page.

Open full augment page →

Cast Changes

  1. Modifies The Vast Untime with: The Vast Untime Augment: Creates a Rift that connects to enemies suffering from Void Status Effect within 15m, doubling debuffs applied by The Vast Untime and maintaining Void Status.
  2. Rank up the augment to unlock the full effect values.
  3. Costs a mod slot (and capacity) — only equip it when the change matters for your loop.

Worth the Slot?

  1. Worth it when the augment’s change is central to how you play Xaku.
  2. Skip it if the base The Vast Untime already does what you need and you’d rather keep the slot for survivability or strength.

Tips & Tricks

  • Read the battlefield first — cast The Vast Untime when it actually solves the room, not on cooldown habit.
  • Pair The Vast Untime with movement and energy economy so you’re not stranded after a big spend.
  • On Steel Path, confirm whether The Vast Untime still carries without strip, Viral, or a squad buff.
  • If you never press 4, it’s the first Helminth candidate on Xaku.

Ability dossier · The Vast Untime

Verified 2026-07-22

Synergies

  • The Vast UntimeXata's Whisper

    Use The Vast Untime to set up Xata's Whisper, or follow Xata's Whisper with The Vast Untime while enemies are vulnerable.

  • The Vast UntimeGrasp Of Lohk

    Use The Vast Untime to set up Grasp Of Lohk, or follow Grasp Of Lohk with The Vast Untime while enemies are vulnerable.

  • The Vast UntimeThe Lost

    Use The Vast Untime to set up The Lost, or follow The Lost with The Vast Untime while enemies are vulnerable.

Mod Scaling

Strength

Improves The Vast Untime’s damage or effect potency where Strength is listed on the ability.

Duration

Extends how long The Vast Untime’s effect lasts.

Range

Range is usually dumpable on The Vast Untime unless you feel the hitbox is too tight.

Efficiency

The Vast Untime costs energy each cast — Efficiency (or strong regen) keeps the loop comfortable on long missions.

Priority

Stack the stats that actually move this ability’s needle, then Efficiency for uptime.

Mission Use Cases

MissionHow to Use It
Steel Path Survival / Defense / DisruptionTest whether The Vast Untime still clears or enables clear when enemies are dense and overlevelled.
Mobile Defense / ExcavationUse The Vast Untime to control or delete the swarm on the objective, then reposition.
Exterminate / Capture Speed RunsCast The Vast Untime only when it saves time — skip it on empty tiles.
Spy / Rescue / Quiet RoutesIf The Vast Untime is loud or forces combat, save it for after the vault; if it’s stealth-friendly, use it to stay safe.

Comparisons

  • VS

    Vs similar tools on other frames — The Vast Untime is tuned for Xaku’s loop — don’t judge it as a standalone subsume without the rest of the kit.

Other Xaku abilities