It adds a chance for chests to open for free (base +10%), helping you save gold.

Community testing suggests a non-linear, independent-roll model (often approximated as 1 − 0.9^n), but exact developer math has not been formally published.

Key

Q: How do you unlock the Key item?

Purchase or open 25 paid chests across your runs.

🟢 COMMON ITEM

Effect: Adds a chance for chests to open for free (base +10%).
Stacking is non-linear (not simple +10% per Key). See the Stacking Note below.

Rarity

Common

Overview

The Key is a simple but powerful economy item that lets you save gold by occasionally opening chests for free. If you’re new to items, browse the full Items database to understand how economy pieces fit into your build.

Stacking Note (Community-verified)

Multiple player tests indicate Key’s free-chest chance uses independent rolls per Key rather than linear addition. A common model is Chance ≈ 1 − (0.9^n), where n is your Key count (e.g., ~65% at 10 Keys). Some wikis report alternative figures (e.g., 50% at 10 Keys). Until developers publish exact math, treat the effect as non-linear and plan accordingly.

How to Unlock Key

Requirement

Purchase or open 25 paid chests across your runs. Paid chest interactions count toward this milestone.

Tips to Unlock Faster

Grab Golden Tome early when possible to boost economy.
Play chest-dense stages and route toward shrines/chests.
Consider Luck-focused runs (e.g., One Lucky Fox) to improve overall loot quality while you farm gold.

Strategy & Synergies

Key shines in economy-forward routes: more free chests = more upgrades with less gold spent.

Credit Card (Green)

Grants Luck when opening chests; pairs naturally with Key’s free-chest procs to snowball reward quality.

See a Luck-centric build

Credit Card (Red)

A chest-interaction damage scaler in many guides; leverage more chest opens for incremental power.

Luck Tome

Luck improves reward quality from level-ups/shrines/drops, complementing Key’s chest volume. Use it to chase better rolls.

Learn what Luck affects

Play Tips

Don’t over-index on Keys early; blend with damage/sustain so you can reach and clear chest events safely.
Because stacking is non-linear, the first few Keys are the most impactful per-copy; evaluate marginal benefit mid-run.

FAQ

Does Luck increase the Key free-chest chance?

Not confirmed by developers. Most media explain Luck as improving reward quality (rarity) from level-ups, shrines and drops, not on-hit/proc chances. Treat Key as independent of Luck’s proc scaling.

What’s the best way to farm the unlock?

Prioritize chest routes, bank gold with economy picks (Golden Tome, movement for faster clears), and consider Luck-focused runs to increase the value of what you find.

Key