Should I upgrade Fasten in Slay the Spire 2?

Compare the upgraded text: Gain an additional 7 Block from Defend cards.. If the upgrade lowers cost, adds damage/block, or enables a combo piece, it is usually high priority.

What builds use Fasten?

Fasten appears in 1 tracked build: Barricade Iron Bastion (A-tier, flex pick).

What character uses Fasten?

Fasten is tagged as a Colorless card. Colorless cards can be picked by any class.

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

Fasten

Colorless · Power · Uncommon · 1 cost

Base

Upgraded

Card text

Gain an additional 5 Block from Defend cards.

Fasten+

Gain an additional 7 Block from Defend cards.

Builds that use Fasten

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

ABarricade Iron BastionIronclad · Flex pick

Build context

Colorless cards splash into every class. Browse the Colorless card pool and pair it with any class build hub for archetypes that want it.

Related cards

Fasten FAQ

Should I upgrade Fasten in Slay the Spire 2?: Compare the upgraded text: Gain an additional 7 Block from Defend cards.. If the upgrade lowers cost, adds damage/block, or enables a combo piece, it is usually high priority.
What builds use Fasten?: Fasten appears in 1 tracked build: Barricade Iron Bastion (A-tier, flex pick).
What character uses Fasten?: Fasten is tagged as a Colorless card. Colorless cards can be picked by any class.

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.