Fusion•Skill

Is Fusion good in Slay the Spire 2?

Fusion is an uncommon Defect skill in Slay the Spire 2. In combat it resolves as: Channel 1 Plasma. It’s a dependable, middle-of-the-pack option, landing at C tier in our rankings.

Across 43 recorded runs, decks running it win 31.6% of the time, comfortably clear of the 18.9% average, by 12.6%. It’s a more selective pick, turning up in just 1.1% of decks that could run it. Defect players keep it in 7.0% of their runs, so it’s a familiar sight in those decks. On average it shows up 1.1 times in the decks that take it.

It performs best next to All for One — together they post a +19.6% swing in win rate. It also has strong chemistry with the relic Red Mask, which moves its win rate by +24.9%. At 2 energy, it’s upgraded in 38.3% of runs and usually joins the deck around floor 17.

Upgraded, it gains -1 EnergyCost, which is why so many decks invest a rest-site upgrade in it. That’s 12 wins, 26 deaths, and 5 abandoned runs with it in the deck. The encounter that most often ends a run carrying it is Aeonglass Boss, which closes out 9.3% of its appearances. Read on for Fusion’s complete synergy, class, and threat breakdown to decide whether it earns a slot in your Defect run.

Best Cards to Pair with Fusion

Ranked by win-rate lift, Fusion performs best alongside All for One (+19.6%), Flak Cannon (+19.6%), and Skim (+19.4%).

All for One+19.6%5 runsFlak Cannon+19.6%4 runsSkim+19.4%6 runsSubroutine+16.6%10 runsScrape+16.4%7 runsTURBO+13.7%9 runs

Based on small co-occurring samples — treat these as early signals, not final verdicts.

Fusion Win Rate by Class

Fusion is played across 2 classes, led by Defect (33.3%) and Necrobinder (0.0%) by win rate.

The Defect33.3%41 runsThe Necrobinder0.0%2 runs

Best Relics for Fusion

Fusion pairs best with the relics Red Mask (+24.9%), Pendulum (+22.8%), and Blood Vial (+19.4%), ranked by win-rate lift.

Red Mask+24.9%8 runsPendulum+22.8%6 runsBlood Vial+19.4%6 runsRegal Pillow+16.4%8 runsBronze Scales+16.4%7 runsEternal Feather+15.8%3 runs

Based on small co-occurring samples — treat these as early signals, not final verdicts.

Fusion Card Details

Fusion is an uncommon skill costing 2 energy; it’s upgraded in 38.3% of runs and usually picked up by floor 17.

Channel 1 Plasma.

Upgrade: -1 EnergyCost

What Ends Runs with Fusion

Fusion’s most common run-enders are Aeonglass Boss (9.3%), Queen Boss (7.0%), and Lagavulin Matriarch Boss (4.7%).

• Aeonglass Boss9.3% of runs
• Queen Boss7.0% of runs
• Lagavulin Matriarch Boss4.7% of runs
• Entomancer Elite4.7% of runs
• Kaiser Crab Boss4.7% of runs

See Also

Compare Fusion with the rest of the best Slay the Spire 2 cards, relics, and classes below.