Synthesis•Attack

Is Synthesis good in Slay the Spire 2?

Synthesis is an uncommon Defect attack in Slay the Spire 2. In combat it resolves as: Deal 12 damage. The next Power you play costs 0 -cost. It currently underperforms most alternatives, sitting at F tier in our Slay the Spire 2 card rankings.

Across 32 recorded runs, decks running it win 20.0% of the time, comfortably clear of the 18.9% average, by 1.1%. It’s a more selective pick, turning up in just 0.8% of decks that could run it. Defect players keep it in 5.3% 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 Adaptive Strike — together they post a +13.3% swing in win rate. It also has strong chemistry with the relic Pendulum, which moves its win rate by +18.5%. At 2 energy, it’s upgraded in 22.9% of runs and usually joins the deck around floor 16.

Upgraded, it gains +6 Damage, which is why so many decks invest a rest-site upgrade in it. That’s 6 wins, 24 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 9.4% of its appearances. Read on for Synthesis’s complete synergy, class, and threat breakdown to decide whether it earns a slot in your Defect run.

Best Cards to Pair with Synthesis

Ranked by win-rate lift, Synthesis performs best alongside Adaptive Strike (+13.3%), Hologram (+11.8%), and White Noise (+11.6%).

Adaptive Strike+13.3%5 runsHologram+11.8%12 runsWhite Noise+11.6%9 runsBoost Away+11.6%10 runsCreative AI+11.3%7 runsEcho Form+10.8%3 runs

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

Synthesis Win Rate by Class

Synthesis is played across 2 classes, led by Defect (20.7%) and Necrobinder (0.0%) by win rate.

The Defect20.7%31 runsThe Necrobinder0.0%1 runs

Best Relics for Synthesis

Synthesis pairs best with the relics Pendulum (+18.5%), Blood Vial (+15.7%), and Red Mask (+15.7%), ranked by win-rate lift.

Pendulum+18.5%3 runsBlood Vial+15.7%4 runsRed Mask+15.7%4 runsKusarigama+13.3%5 runsBronze Scales+10.8%4 runsPotion Belt+10.8%3 runs

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

Synthesis Card Details

Synthesis is an uncommon attack costing 2 energy; it’s upgraded in 22.9% of runs and usually picked up by floor 16.

Deal 12 damage. The next Power you play costs 0 -cost.

Upgrade: +6 Damage

What Ends Runs with Synthesis

Synthesis’s most common run-enders are Aeonglass Boss (9.4%), Queen Boss (6.3%), and The Obscura Normal (6.3%).

• Aeonglass Boss9.4% of runs
• Queen Boss6.3% of runs
• The Obscura Normal6.3% of runs
• Entomancer Elite6.3% of runs
• Lagavulin Matriarch Boss6.3% of runs

See Also

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