- Upgrade priority: Focus resources on Sans and Undyne, the strongest long-term carries.
- Early value: Papyrus and Frisk carry early stages cheaply until better units arrive.
- Trait rerolls: Spend rerolls on permanent core units first, never on temporary picks.
- Positioning rule: Upgrading one well-placed unit beats spreading levels across weak ones.
- Team balance: Combine damage, support, and coverage before chasing pure rarity.
Upgrade Priority Overview
Upgrading units in Undertale Adventures X is the fastest way to power up your team, but resources are limited. Every gem, coin, and reroll you spend on the wrong unit is progress you lose. The key is to judge units by their complete battle contribution — damage consistency, placement value, and how long they stay relevant — rather than rarity alone.
Concentrated upgrades on your best-positioned unit almost always outperform a wide field of under-leveled units. Upgrade before you expand.
The table below ranks the core units by upgrade value across the game's progression:
| Unit | Role | Upgrade Priority | Best Content | Key Strength |
|---|---|---|---|---|
| Sans | Damage & control | ★★★★★ | Late-game, boss stages | High impact when enemies survive multiple attack cycles |
| Undyne | Sustained damage | ★★★★★ | General progression | Consistent output across repeated waves |
| Papyrus | Early/mid damage | ★★★☆☆ | Opening stages | Reliable coverage before premium units |
| Toriel | Support/defense | ★★★★☆ | Sustained-wave stages | Stabilizes teams under pressure |
| Frisk | Starter utility | ★★☆☆☆ | First stages | Cheap, easy to understand placement |
A strong roster combines reliable early damage, upgraded late-game carries, and utility that handles crowded waves or powerful enemies. Never sacrifice your whole team's balance just to obtain one premium unit.
Unit Roles and What Worth Upgrading
Each unit in Undertale Adventures fills a specific battlefield role. Matching your upgrade investment to that role is what separates efficient players from those who waste resources.
Damage Carries (Sans, Undyne)
- Highest upgrade priority
- Scale strongly with levels
- Justify reroll and resource spending
- Anchor late-game and boss content
Support (Toriel)
- Upgrade when team survives poorly
- Pairs with main damage dealers
- Protects your investment in carries
- Best in complete teams, not solo
Transitional (Frisk, Flowey, Papyrus)
- Upgrade only as much as needed
- Cover early waves cheaply
- Replace once stronger options perform better
- Skip trait rerolls entirely
Detailed Upgrade Value Table
| Unit | Attack Profile | Upgrade Value | Team Combination |
|---|---|---|---|
| Sans | Repeated attacks on long routes, upgraded effects | High for difficult content | Pair with early unit for safe upgrading; add second damage source for multi-lane stages |
| Undyne | Consistent pressure, handles dense waves | High for general progression | Place near long route sections; combine with Papyrus or Frisk |
| Papyrus | Standard wave clearing | Medium-high early, drops later | Use behind a frontline placement for more attack time |
| Toriel | Stability and protection | High in survival-heavy stages | Place near main damage group; pair with Undyne or Sans |
| Frisk | Basic placement learning | Low beyond opening stages | Use as opening placement while saving for stronger units |
Do not dump upgrade resources into units you plan to replace soon. Frisk and Flowey are useful, but every coin spent on them is a coin not going toward Sans or Undyne. Upgrade transitional units only enough to clear the stage in front of you.
Step-by-Step Upgrade Path
Follow this progression path to upgrade units efficiently from your first stage to high-difficulty content.
Build a Functional Starter Team
Enter the lobby, review your units, and select a balanced team with at least one damage dealer and one support option. Use Frisk and Papyrus to clear opening stages while saving resources. A balanced team gives you room to recover from leaks and difficult waves.
Establish Stable Early Income
Place units near the first choke point — corners, bends, and shared paths where enemies stay in range longest. Add a second unit only after the opening wave is stable, and keep currency in reserve for the next wave.
Upgrade Before Expanding
Improve your best-positioned unit before placing several weak ones. Prioritize range or damage upgrades when the next wave gets difficult, and focus on units covering long sections of the path. Sell or reposition inefficient units when the stage allows it.
Invest in Core Carries
Once you obtain Sans or Undyne, shift all major upgrade spending to them. Reinvest completed-stage rewards into these permanent carries, and test new units in normal content before taking them into difficult stages.
Specialize for Difficult Content
Build around each stage's specific threats. Use your best-traited units, adjust placement per map, and reserve rerolls for core damage dealers first, followed by essential supports and difficult-stage specialists.
Progression becomes smoother when upgrades are based on actual battle performance instead of rarity alone. Watch which units consistently contribute during full waves — those are your upgrade targets.
Traits and Summoning: Supporting Your Upgrades
Upgrading units works best when paired with smart trait and summon decisions. Traits provide additional combat advantages — damage, attack speed, range, or survivability — that change how efficiently a unit performs during a stage.
Trait Spending Priorities
| Trait Focus | Combat Benefit | Recommended Unit | Resource Priority |
|---|---|---|---|
| Damage-focused | Better clearing and tougher-target damage | Main damage dealers (Sans, Undyne) | High for permanent carries |
| Range / attack speed | Better coverage and placement flexibility | Multi-lane and repeated-attack units | Prioritize when it fixes a placement weakness |
| Support consistency | Survivability, coverage, uptime | Toriel and utility units | Reroll only after support role is reliable |
| Reroll planning | Larger team improvement per resource spent | Core damage dealers first | Never spend on units you will replace |
Use rerolls selectively. Lock in a useful trait when it meets the unit's role, then move to the next priority unit. A carefully chosen reroll target produces a bigger team improvement than spreading resources across many incomplete units.
Summon Resource Planning
When summoning new units, follow these rules so your upgrade budget stays healthy:
| Rule | Action | Why It Matters |
|---|---|---|
| Check roster first | Identify missing roles before summoning | Filling a gap beats duplicating a role |
| Keep a reserve | Set a minimum currency floor | Routine summons drain upgrade funds |
| Evaluate rarity in context | Compare role and upgrade potential | Rarity alone does not replace coverage |
| Keep duplicates | Hold until mechanics are confirmed | Duplicates may feed enhancement systems |
| Save for banners | Stop routine summons once functional | Limited pools and new releases need reserves |
Mode-by-Mode Upgrade Targets
Different game modes reward different upgrade choices. Match your investment to the content you are farming.
| Mode | Objective | Upgrade Focus | Team Approach |
|---|---|---|---|
| Story stages | Advance and unlock content | Balanced damage and coverage | Reliable damage plus one pressure handler |
| Resource stages | Farm currency and materials | Clear speed and survivability | Consistent builds over experimental ones |
| Challenge content | Test optimized teams | Max carries with best traits | Build around stage-specific threats |
| Limited events | Complete event objectives | Objective-maximizing units | Check event rules before committing |
Patch notes can change unit performance, traits, and progression costs. Reevaluate your upgrade priorities whenever a balance adjustment lands — a previously weaker unit may become worth the investment.
Upgrade Milestones:
- Clear all opening stages with starter units
- Establish a stable income and upgrade rhythm
- Obtain and fully upgrade one core carry (Sans or Undyne)
- Lock a useful trait on your main damage dealer
- Build a reserve for limited banners and events
FAQ
Q: Which unit should I upgrade first in Undertale Adventures?
If you have Sans or Undyne, prioritize them — both are long-term carries with high upgrade value. Before that, upgrade Papyrus just enough to clear early stages, since he will eventually be replaced by stronger units.
Q: Should I upgrade multiple units at once?
Generally no. Concentrated upgrades on your best-positioned unit are easier to manage and more effective than a wide field of under-leveled units. Expand only after your core unit handles waves comfortably.
Q: When should I spend trait rerolls?
Only on units confirmed as part of your long-term team. Start with core damage dealers like Sans and Undyne, then essential supports. Never reroll transitional units such as Frisk or Flowey.
Q: How do duplicates affect my upgrade plans?
Keep duplicates until you confirm whether they feed enhancement, progression, or exchange systems. Do not discard or convert them before checking their intended use, as they may be required for upgrades.