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 currently underperforms most alternatives, sitting at D tier in our Slay the Spire 2 card rankings.

Across 266 recorded runs, decks running it win 20.8% of the time, comfortably clear of the 13.8% average, by 7.0%. It’s a more selective pick, turning up in just 1.3% of decks that could run it. Offer data is close to a wash — 13.9% of offers taken, 20.9% for runs that picked it against 19.1% for runs that skipped, a pick lift of just +1.7% over 211 decided runs. Defect players keep it in 5.6% 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 Scrape — together they post a +27.8% swing in win rate. It also has strong chemistry with the relic Bag of Preparation, which moves its win rate by +26.3%. At 2 energy, it’s upgraded in 34.8% of runs and usually joins the deck around floor 16.

Upgraded, it gains -1 EnergyCost, which is why so many decks invest a rest-site upgrade in it. That’s 55 wins, 209 deaths, and 2 abandoned runs with it in the deck. The encounter that most often ends a run carrying it is Aeonglass Boss, which closes out 9.0% 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.

Pick or Skip: Fusion

Out of 1582 recorded offers Fusion is taken 13.9% of the time, and taking it is worth +1.7% in pick lift — 20.9% for runs that picked it against 19.1% for runs that skipped, across 211 decided runs.

Taken 220 times out of 1582 offers.

Pick rate when offered counts offers, not runs: out of every time the game put this in front of a player, how often it was taken. It is not the same number as the share of runs that end up containing it.

Pick lift is the sample-adjusted gap between runs that took the option and runs that passed on it. It is the fair way to rank choices, because raw win rates put the smallest samples on top.

When to Pick Up Fusion

Fusion is strongest when it joins the deck in Act 3, where runs win 62.5% across 32 runs — one of 4 recorded pickup windows.

Win rate of runs by the act Fusion entered the deck. Acts that have not reached the sample floor show their run count only.

Best Cards to Pair with Fusion

Ranked by win-rate lift, Fusion performs best alongside Scrape (+27.8%), Supercritical (+22.8%), and Creative AI (+22.2%).

Scrape+27.8%21 runsSupercritical+22.8%37 runsCreative AI+22.2%32 runsFlak Cannon+17.9%16 runsBulk Up+17.8%29 runsOverclock+16.8%38 runs

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

Fusion Win Rate by Class

Fusion is drafted only by the Defect, where it holds a 21.0% win rate across 254 runs.

The Defectappears in 5.6% of its runs (254 tracked)

Best Relics for Fusion

Fusion pairs best with the relics Bag of Preparation (+26.3%), Data Disk (+25.9%), and Horn Cleat (+22.3%), ranked by win-rate lift.

Bag of Preparation+26.3%39 runsData Disk+25.9%34 runsHorn Cleat+22.3%25 runsRed Mask+21.9%37 runsBronze Scales+21.9%37 runsOrnamental Fan+21.4%21 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 34.8% of runs and usually picked up by floor 16.

Channel 1 Plasma.

Upgrade: -1 EnergyCost

What Ends Runs with Fusion

Fusion’s most common run-enders are Aeonglass Boss (9.0%), Queen Boss (6.0%), and Kaiser Crab Boss (5.3%).

• Aeonglass Boss9.0% of runs
• Queen Boss6.0% of runs
• Kaiser Crab Boss5.3% of runs
• Knowledge Demon Boss4.9% of runs
• Entomancer Elite3.4% of runs

See Also

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