Undertale Adventures X Evolution Guide: How to Evolve Units and Farm Souls Fast

Evolution is the biggest power spike in Undertale Adventures X, and it is also the system that confuses the most new players. This Undertale Adventures X evolution guide breaks down what evolution actually changes, which resources you need to feed it, and how to spend those resources without torching a week of grinding. Whether you are stuck on a mid-game chapter or just want your favorite Undertale-inspired unit to hit harder, the advice below will keep your squad moving forward instead of standing still.

How Evolution Works in Undertale Adventures X

Undertale Adventures X is a Roblox tower defense game built around recognizable Undertale characters, and your units are your most important asset. You summon them with Souls, which are crafted by combining Soul Fragments, and you strengthen them through a few separate systems that players often blur together: leveling, evolving, and trait rerolling.

Evolution is the permanent upgrade path. In most tower defense games of this style — and per player experience in this one — evolving a unit consumes currency and specific materials to unlock a stronger form. That new form usually comes with higher base stats, better scaling as you level it again, and sometimes an upgraded or reworked ability.

The exact requirements live inside each unit's evolution panel, and they can change between updates. Always read that panel before you start spending. A unit that looks cheap to evolve at low levels may need rare materials once you reach the final tier.

Evolution vs. leveling vs. traits

The takeaway: leveling is temporary power, evolution is permanent power, and traits are the fine-tuning layer you apply on top.

Evolution Resources and Where to Farm Them

Before you chase evolution, understand the economy. Community reports consistently point to Souls as the bottleneck, because the same currency that summons new units also feeds your upgrades. Spending everything on summons is the fastest way to stall your progression.

Two habits separate efficient players from stuck ones. First, bank a reserve of Souls before a new banner or update drops. Second, only reroll traits on units you have already committed to evolving — rerolls spent on a placeholder unit are rerolls wasted.

If you are short on currency, codes are the cheapest top-up available. GamesRadar maintains a regularly updated Undertale Adventures X codes list that tracks which rewards are still live, which is worth checking before you grind another hour.

Step-by-Step: Evolving a Unit Without Wasting Souls

The order you do things in matters more than raw playtime. Follow this sequence and you will rarely waste a resource.

A quick note on step 6: many players reroll a trait on a base unit, evolve it, and then discover the trait no longer fits the evolved ability. Do the evolution first, then chase the trait you actually want.

Evolution Priorities: Which Units Deserve Your Souls

Not every unit is worth evolving, and the ones that are depend on your roster. Still, the priority logic is consistent across tower defense games like this one.

Common evolution mistakes to avoid

• Evolving a unit you never use just because the materials were available.
• Rerolling traits before evolving, which wastes Trait Rerolls on a temporary form.
• Skipping the level requirement check, then discovering you are short of Souls mid-evolution.
• Ignoring codes, which are free Souls and rerolls that cost nothing but a few seconds.
• Abandoning a half-built carry to chase a shiny new summon from the latest banner.

Trait Rerolls, Codes, and Free Resources

Trait Rerolls are the cheapest way to squeeze extra damage out of a unit you have already evolved. You use them in the upgrades area, where the rolled bonus is applied to your team's stats. Player experience suggests prioritizing offensive traits on your carry and utility traits on support units.

Codes are the other free source of these resources. As of mid-October 2026, the community-tracked list includes one active code:

Several older codes have already expired, including THANKYOUFORWAITING, 2KCCU!, FREESTUFF!, TRADINGSOON!, and MONEYTONIGHT. Codes in this game can die within hours of release, so redeem anything you see immediately rather than saving it for later.

To reach the redemption box, open the main lobby and click the Codes button on the right-hand side of the screen.

Frequently Asked Questions About This Undertale Adventures X Evolution Guide

What is the fastest way to farm Souls in Undertale Adventures X?

Combine every Soul Fragment you collect, replay the highest chapter you can clear reliably, and redeem codes the moment they go live. Codes are the single fastest injection of Souls, because they cost nothing but the ten seconds it takes to type them in.

Do I need duplicate units to evolve a unit in Undertale Adventures X?

Requirements vary by unit and by evolution tier, and they change between updates. Some evolutions ask for materials rather than duplicates. Check the unit's own evolution panel — it lists exactly what that specific unit needs, so you never have to guess.

Should I reroll traits before or after evolving?

After. Traits are applied to the form you are using, so rerolling a base unit and then evolving it usually wastes the roll. Evolve first, confirm the new ability, then spend Trait Rerolls to match that ability.

Will this Undertale Adventures X evolution guide stay accurate after updates?

The core loop — farm Souls, evolve one carry at a time, reroll traits afterward — is stable and unlikely to change. Specific costs, materials, and code rewards are the parts that shift, so treat the tables here as a framework and confirm the numbers in-game before you commit resources.

Stick to the sequence, protect your Soul reserve, and evolve one unit at a time. That approach will carry you through far more chapters than a scattered roster ever will.