Undertale Adventures X Units Codex: Roles, Acquisition and the Roster System

Every unit in Undertale Adventures X is an Undertale character pulled into tower defense service, and the roster is the game's real character sheet — wider and better-shaped rosters clear deeper waves, and the systems around the roster (summoning, rerolling, materials) are how a collection grows from a first pull into a lineup that carries late-game runs. This codex is the framework page: how the roster is organized, what each combat role does, and every verified channel through which units and their materials enter your account. It deliberately does not rank individual characters — the best units guide handles selection strategy, and this page handles the system both of those decisions live inside.

How the Roster Is Organized

The premise does the heavy lifting: the units are Undertale characters, which means the roster grows the way the franchise's cast does — familiar faces filling familiar combat shapes. A unit in this game is defined by three layers, and reading a unit means reading all three. The character is who the unit is and the kit it brings. The soul layer is the core property set the Soul Reroll system modifies — the layer that sets what a unit can fundamentally become. And the trait layer is the modifier set the Trait Reroll system tunes — the layer that makes two copies of the same character play differently in practice.

That layered structure is why this codex talks in roles rather than names. The game is young and its roster is actively expanding, which means any fixed name-by-name ranking dates itself within an update or two. The role framework below survives every roster expansion, because every new unit arrives already sorted into one of the three shapes players actually build around.

The Three Combat Roles

Read any lineup through three profiles, and the gaps become visible at a glance.

Main damage dealers are the single-target backbone of a defense. Their job is concentrated output on the threats that matter — the wave's carry enemies, the ones that slip past everything else and end runs. A lineup without a reliable main damage profile loses to exactly one thing: the single enemy your area damage chipped but never killed. When you place one, the placement rule from the beginner's guide applies hardest — put main damage where enemies spend the most time in range.

Area-clearing units are the wave erasers. Their job is breadth: hitting everything crossing a stretch of path at once, thinning crowds before the main damage dealers have to spend their attention on them. Area clear is what makes heavy waves survivable and light waves cheap, and a roster that stacks only single-target output discovers its ceiling the first time a dense wave walks through it.

Support units are the multipliers. Their job is not to top the damage screen but to make the units who do perform better — through the buffs, utility and coverage the game attaches to the support profile. Supports are the least flashy slot on a lineup and the most commonly skipped by new players, which is a mistake: a multiplied main damage dealer outperforms an unmultiplied one without any rerolls spent. The strongest lineups are not three damage profiles — they are one of each role, shaped to the map.

How Units and Materials Enter Your Account

Four verified channels feed the roster, and they rank in a specific order for a new account.

Codes first. The working codes table is the fastest roster fuel in the game: the current milestone codes deliver 50 Trait Rerolls and 5,555 Souls each — the currencies the reroll systems consume — while the Halloween code adds Soul Fragments, Perfect Souls and a Bravery Vial on top of its own Souls-and-Gold line. The food items codes deliver alongside (Butterscotch Pie, Glamburgers, Temmie Flakes and the rest) are the game's Undertale-flavored consumable layer. None of this summons a unit by itself, but all of it funds the summoning and improvement loop that does.

The summoning system second. Units enter your account through the game's summon mechanic, fueled by the resources codes and play provide. Summons are probabilistic, which means roster growth is a volume game: more summons, more copies, more chances at the profiles your lineup lacks. This is the same reason hoarding summon currency is a beginner trap — currency that sits is roster growth that does not happen.

Play third. Waves, runs and the lobby farming route keep the resource side of the loop fed between code drops, and the farming guide covers the most efficient verified route.

Events fourth. Seasonal events — Halloween is the live example as of October 2026 — ship their own reward tracks and materials, which is where event-specific additions to the roster economy surface.

FAQ

What are units in Undertale Adventures X?

Undertale characters used as tower defense units. Each unit is defined by its character kit, its soul layer (modified by Soul Rerolls) and its trait layer (modified by Trait Rerolls), and fills one of three combat roles: main damage, area clear, or support.

Is there a definitive list of every unit with stats?

Not on this page, on purpose. The roster is young and actively expanding, and a stat list that cannot be verified against the live game is fabrication by another name. This codex documents the verified system — roles, layers, acquisition — and lets the role framework do the work name-chasing lists fake.

How many units do I actually need?

One competent unit per role covers the early game, and depth comes later. The selection order — which slots to upgrade first — is laid out in the best units guide, and it starts with your main damage dealer.

Where do Trait Rerolls come from?

Primarily codes — the milestone line pays 50 per code — supplemented by play. That concentration is why the codes page is a roster page too: an account that skips codes is an account that cannot afford to tune its traits.