Should I upgrade Fusion in Slay the Spire 2?

Compare the upgraded text: Cost changes from 2 to 1. If the upgrade lowers cost, adds damage/block, or enables a combo piece, it is usually high priority.

What builds use Fusion?

Fusion appears in 1 tracked build: Overcharge Detonation (A-tier, core card).

What character uses Fusion?

Fusion is tagged as a Defect card. See the Defect build hub for archetypes that care about it.

Updated for Data 2026-03-17Early Access — numbers may shift with patches.

Fusion

Defect · Skill · Uncommon · 2 cost

Base

Upgraded

Card text

Channel 1 Plasma.

Fusion+

Cost changes from 2 to 1

Builds that use Fusion

Archetypes that draft this card in real runs, with the role it plays.

AOvercharge DetonationDefect · Core card

Keywords

Channel

Build context

See the Defect build hub for archetypes that feature this card in real runs.

Related cards

Fusion FAQ

Should I upgrade Fusion in Slay the Spire 2?: Compare the upgraded text: Cost changes from 2 to 1. If the upgrade lowers cost, adds damage/block, or enables a combo piece, it is usually high priority.
What builds use Fusion?: Fusion appears in 1 tracked build: Overcharge Detonation (A-tier, core card).
What character uses Fusion?: Fusion is tagged as a Defect card. See the Defect build hub for archetypes that care about it.

Patch history

SpireForge snapshots card text from Untapped exports dated 2026-03-17. When Mega Crit ships a balance patch, we re-run the scraper and refresh every affected URL—see /patches for the editorial log.