Signal Boost•Skill

Is Signal Boost good in Slay the Spire 2?

Signal Boost is a rare Defect skill in Slay the Spire 2. In combat it resolves as: The next Power you play is played an additional time. It’s a dependable, middle-of-the-pack option, landing at C tier in our rankings.

Across 138 recorded runs, decks running it win 29.2% of the time, comfortably clear of the 13.9% average, by 15.3%. It’s a more selective pick, turning up in just 1.2% of decks that could run it. Offer data backs the pick — taken 32.5% of the time it is shown, with 33.3% for runs that took it against 23.2% for runs that did not, a +9.3% pick lift across 111 decided runs. Defect players keep it in 7.8% of their runs, so it’s a familiar sight in those decks. On average it shows up 1.2 times in the decks that take it.

It performs best next to Genetic Algorithm — together they post a +22.4% swing in win rate. It also has strong chemistry with the relic Red Mask, which moves its win rate by +23.4%. At 1 energy, it’s upgraded in 35.5% 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 40 wins, 97 deaths, and 1 abandoned runs with it in the deck. The encounter that most often ends a run carrying it is Knowledge Demon Boss, which closes out 5.8% of its appearances. Read on for Signal Boost’s complete synergy, class, and threat breakdown to decide whether it earns a slot in your Defect run.

Pick or Skip: Signal Boost

Out of 372 recorded offers Signal Boost is taken 32.5% of the time, and taking it is worth +9.3% in pick lift — 33.3% for runs that picked it against 23.2% for runs that skipped, across 111 decided runs.

Taken 121 times out of 372 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 Signal Boost

Signal Boost is strongest when it joins the deck in Act 2, where runs win 51.2% across 42 runs — one of 2 recorded pickup windows.

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

Best Cards to Pair with Signal Boost

Ranked by win-rate lift, Signal Boost performs best alongside Genetic Algorithm (+22.4%), Echo Form (+20.6%), and Supercritical (+20.6%).

Genetic Algorithm+22.4%17 runsEcho Form+20.6%24 runsSupercritical+20.6%24 runsDefragment+14.3%22 runsFeral+13.4%18 runsHailstorm+13.0%23 runs

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

Signal Boost Win Rate by Class

Signal Boost is drafted only by the Defect, where it holds a 28.2% win rate across 131 runs.

The Defectappears in 7.8% of its runs (131 tracked)

Best Relics for Signal Boost

Signal Boost pairs best with the relics Red Mask (+23.4%), Pendulum (+20.6%), and Happy Flower (+20.5%), ranked by win-rate lift.

Red Mask+23.4%26 runsPendulum+20.6%22 runsHappy Flower+20.5%20 runsWar Paint+20.5%20 runsBag of Preparation+18.9%21 runsMeal Ticket+18.6%17 runs

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

Signal Boost Card Details

Signal Boost is a rare skill costing 1 energy; it’s upgraded in 35.5% of runs and usually picked up by floor 16.

The next Power you play is played an additional time.

Upgrade: -1 EnergyCost

What Ends Runs with Signal Boost

Signal Boost’s most common run-enders are Knowledge Demon Boss (5.8%), Kaiser Crab Boss (5.8%), and Test Subject Boss (5.1%).

• Knowledge Demon Boss5.8% of runs
• Kaiser Crab Boss5.8% of runs
• Test Subject Boss5.1% of runs
• The Obscura Normal3.6% of runs
• Mytes Normal3.6% of runs

See Also

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