← All Vault Hunters

Borderlands 4 Vex guide — the only capstone that gives you a second augment slot

Published: 9/4/2026 · As of Version 1.9

Unofficial fan resource. Not affiliated with Gearbox Software, 2K or Take-Two Interactive.

Vex is one of the base-game Vault Hunters and the series’ returning Siren archetype — but built as a summoner rather than the crowd-control role earlier Sirens filled. 2K’s material paints her as someone acutely attuned to other people’s suffering, pessimistic about the world and still committed to helping.

The three action skills

The clone terminology — Phase Clone for the category, Specter for the shooting type, Reaper for the melee type — was confirmed from in-game display on 2026-07-24.

The three skill trees

What only Vex does — a second augment slot

The default across Borderlands 4 is one augment plus one capstone per action skill. Exactly two Vault Hunters in the game change that default: Vex and C4SH.

Vex’s version is Dark Pact, the capstone at the end of branch 3 in The Fourth Seal. It is unusual because the capstone itself grants the extra augment slot.

All confirmed in-game on 2026-07-24.

Two things close the obvious loopholes. Gear — class mods, enhancements, legendaries — never adds augment slots; only the skill tree does. And class mod bonus skill points do not count toward tier unlocks (confirmed 2026-07-21), so you cannot pad your way to Dark Pact early. The 25 points come out of your own pocket.

The unlock rules themselves are fully verified here.

Your gun decides your damage type

Vex’s trait is Phase Covenant: she attunes to the element of the gun she is currently holding, and her action skill and melee damage convert to that type.

That matters because the trees carry Attunement passives for five separate elements, scattered across all three. Vex is designed so that one point allocation covers multiple elements and you switch by swapping weapons.

All confirmed 2026-07-24. The cryo one (Icy Attunement) is still unlocated.

What we confirmed in-game

Skills with measured coefficients (three only)

Confirmed 2026-08-15. Every other passive’s coefficient is still unknown.

A worked capstone route

Unsealed sits at the end of branch 3 in Here Comes Trouble. 15 in common + 10 inside that same branch (Shocking Attunement 5 + Grave Current 5) = 25 points reached the capstone tier, and Unsealed equipped for 0 points (confirmed 2026-07-20).

Tier positions and maximum ranks

Roughly 80 nodes have had their tier position and maximum rank confirmed in-game (2026-07-24, some 2026-07-20). There are nine capstones across three trees; six of them have confirmed in-game display names, including Dark Pact.

From official patch notes

The 2025-10-23 patch changed Unsealed’s per-stack damage via the Apex Beast augment from 10% to 15%.

What we have not confirmed

• None of the three action skills has confirmed numbers — phase explosion damage, clone health decay, cooldowns, warp area damage, badass duration
• Phase Covenant’s conversion multiplier is unknown
• Apart from the three above, no passive coefficient is verified
• The in-game name for Incarnate does not match the official site. 2K’s Japanese page uses a translated name; our own record from the game differs. Until we re-check the in-game display we are keeping the English name here
• Whether the per-node prerequisites found on Rafa and Harlowe also exist on Vex has not been investigated
• In-game nodes display as icons without names, so the exact mapping of every tile within a tier is incomplete