Chests and altars
The seven chest types, what's inside each one, and how challenge altars work, in v0.9.16.
The seven chest types
Chest positions on each map are fixed, but the type at each position is re-rolled every run using these odds — except a few markers with a fixed type (two Legendary chests in the sulfur pools of the Corrupted Desert, and several in the dungeons). The seventh, the artifact chest, never takes part in that roll: it only appears on hand-placed spots. Chests reappear when you advance a phase:
| Type | Share | What it gives |
|---|---|---|
 Mix | A roll on the Mix table: contents + gold + some Mithril. | |
 Gamble Mix | Coin flip: loot with extra Luck, or a horde instead. | |
 Common | A reward of exactly its rarity, plus gold for its tier. | |
 Uncommon | A reward of exactly its rarity, plus gold for its tier. | |
 Rare | A reward of exactly its rarity, plus gold for its tier. | |
 Legendary | A reward of exactly its rarity, plus gold for its tier. | |
 Artifact | Always an artifact; if none is eligible for you, a passive item. |
The artifact chest (since v0.9.13) is a slightly bigger Mix chest with a green “?”. It always gives one artifact: first the rarity is rolled with the artifact weights —common 50 · uncommon 30 · rare 15 · legendary 5—, only among the rarities where you still have one available, then one at random of that rarity. If no artifact is eligible for you (all 10 slots full and maxed), it gives a Rare or Legendary passive item; failing that, any passive item; and failing that, just gold (30–60). There are two today, both in the Dwarven Dungeon: behind the pagoda of the guardian camp in phase 1, and at the south bridge door in phase 2.
Inside the Mix chest
The Mix table first rolls the category — runes ≈33% · passives ≈45% · artifacts ≈18% · infusions ≈4% — then the specific item by weight. Besides the contents, every opening drops 4–24 gold and 0–5 Mithril (usually 0–2), and very rarely a Reroll Token.
The gamble chest
It's a coin flip: 50% of the time it drops a Mix's loot with +0.6 Luck; the rest of the time it throws a horde of 10 + 1 per phase (max 16) drawn from the spawn table.
Chests that aren't on the ground
- Every boss —phase or dungeon boss— drops 2 Legendary chests on death and pays 25 Mithril.
- The miniboss drops a chest: guaranteed the first time in a phase, 70% the following times, and ≈14% during overtime.
- Every completed challenge altar grants a Mix chest.
Challenge altars
Activate it and hold on for 30 seconds inside the zone (7 m radius). Progress pauses if you leave and only cancels if you move more than 40 m away. While it runs, the altar adds extra enemy waves every 2.5 s (3 per wave), drawn from the spawn table ignoring the phase and skewed toward the dangerous types from late phases. On completion: a Mix chest, and the altar is spent.
Verified against game v0.9.16.