Catch a Monster Enhancement Guide: EM%, Chaos Potion & Arcane Stones (2026)

Making your monsters stronger in Catch a Monster is not just about rank — it is about understanding the layered enhancement systems that can take a good monster and make it exceptional. This guide covers EM%, Chaos Potions, Potential Serums, and the Arcane Stone system for B-to-A rank fusions.

The EM% System (Enhancement Modifier)

EM% stands for Enhancement Modifier. It is a stat multiplier applied to your monster after evolution. A higher EM% means better overall stats.

Practical targets: Aim for 190%+ for your main team monsters. For your absolute best monster (e.g., Eclipse Knight A+10), try to reach 210%+.

How EM% is Set

EM% is determined when a monster is evolved It cannot be seen before evolving After evolving, EM% can only be changed using a Chaos Potion

Chaos Potion — How to Improve EM%

A Chaos Potion rerolls your evolved monster's EM% to a new random value within the 140–220 range.

Key facts: The new value is completely random — it can be higher OR lower than your current EM% The community average is 6–8 Chaos Potions before hitting a satisfying EM% Some players have spent 15+ potions without reaching their target The minimum result is always 140% — you cannot go below the floor

Strategy: Decide on your target EM% before you start (190% is a good stopping point for most players). Use potions one at a time; stop the moment you hit or exceed your target.

How to Get Chaos Potions

Event Boss drops (rare) Event Shop during limited events Craft using Reversion Potions as a component (community-confirmed recipe) Cannot be purchased directly from the permanent shop

Potential Serums — Boosting Stats Directly

Potential Serums directly boost your monster's potential stats, independent of EM%.

Important: Do not dump all your Potential Serums on one monster immediately. The success rate degrades per use, so spreading them over time gives better value. Community advice: use no more than 3–4 serums on a single monster before moving on to the next.

Arcane Spark Stones — B-Rank to A-Rank Fusion

To ascend a monster from B-rank to A-rank, you use the fusion system with Arcane Spark Stones.

Requirements for One B→A Fusion

Arcane Spark Stone Costs (Updated February 2026)

The Arcane Stone price was reduced from 900 to 500 Tower Gems in the February 20, 2026 update after heavy community feedback. This is a significant F2P improvement.

Time Budget for One A-Rank Monster

Reality check: If you also buy Potential Serums (500 each) and Rift Portals, the actual time to save 8,500 gems for one fusion is closer to 1 week for an average player.

Weekly Planning Guide

With 32 Arcane Stones available per week at 500 gems each: Buying all 32 stones costs 16,000 Tower Gems/week At ~4,800/day, you earn ~33,600 Tower Gems/week Budget ~17,600 remaining for Potential Serums and other purchases

The A+10 Ascension Path (Eclipse Knight)

Once your monster is A-rank, use individual Arcane Spark Stones to ascend it (not the 17-stone fusion): Each "+1" level = 1 Arcane Spark Stone Maximum: A+10 (10 stones for max ascension) A+10 significantly enhances the monster's base stats and skill potency

At A+10, Eclipse Knight's shield becomes strong enough to protect the team through Spire floors 100+ and Red Rifts.

Tips & Common Mistakes

Do not chaos-potion a low-rank monster: Only use Chaos Potions on your A-rank or S-rank monsters. Wasting potions on B-rank is inefficient. Use Reversion Potion carefully: This reverts an evolution back to base form. There is a known bug where pets occasionally disappear after using it. Do not use on your best monsters until the bug is confirmed fixed. Stack up before potioning: Save 6–10 Chaos Potions before you start rerolling so you can quickly hit your target EM% in one session. Arcane Stones are the main bottleneck: Plan your weekly Tower Gem spending around securing all 32 Arcane Stones before buying other items.

For Tower Gem farming tips, see Endless Spire Guide. For the best monsters to enhance, see Tier List.*