The Soot rune, as the game draws it on the gear screen.

Rune · tier 1 · from floor 1

Soot

Set in a weapon: +3% swing speed. Set in an off-hand or armour: +2% move speed.

Play

Drops from floor 1 down.

What it adds

Tier
1
First floor
1
In a weapon
+3% swing speed
In an off-hand or armour
+2% move speed
Smith’s price to empty
30 gold

The line counts once per socket it sits in: two Soot runes in one weapon give twice +3% swing speed. On the gear screen, tap a rune, then an empty socket. A set rune stays: the only way out is the Smith in town, who empties a socket for gold (30 for a tier 1 rune, up to 90 for tier 5) and destroys the rune; the socket stays, ready for another. A rune adds its weapon line in a weapon and its other line in an off-hand or armour.

Where it drops

A kill drops a rune 50% of the time for a boss, 6% for an elite and 0.4% for any other monster. Which rune it is depends on the floor: tier 1 runes drop from floor 1, tier 2 from 5, tier 3 from 10, tier 4 from 16 and tier 5 from 22, and among the tiers a floor allows each rune is weighted 32 at tier 1, 16 at tier 2, 8 at tier 3, 4 at tier 4 and 2 at tier 5, so a deeper tier never becomes common. Runes you carry are banked when you go home through a portal; a fall loses them with the items you carry. On floor 1, where it first can drop, 25.0% of the runes that drop are Soot; deeper, the higher tiers join the draw and its share shrinks.

The chance a kill drops Soot, by floor
FloorsShare of runesBoss killElite killOther kill
1–425.0%12.5%1.50%0.100% (1 in 1,000)
5–918.2%9.1%1.09%0.073% (1 in 1,375)
10–1516.0%8.0%0.96%0.064% (1 in 1,562)
16–2115.4%7.7%0.92%0.062% (1 in 1,625)
22 and deeper15.1%7.5%0.91%0.060% (1 in 1,656)

“Share of runes” is the chance that a rune that drops is Soot; the other columns multiply it by each kill’s chance of dropping a rune at all.

Inscriptions

Soot is part of 2 inscriptions: Cinderwake (second of 3, for the Mage) and Lantern Debt (second of 2, for any hero). An inscription is cut when an item has exactly as many sockets as the inscription has runes, every socket filled, in the inscription’s order. A 3-socket chest with Brine and Quill in its first two sockets spells nothing: the count must match too. The inscription’s power works only for the hero it is cut for; on anyone else the item keeps its rune stats and the power sleeps.

Other runes

The other tier 1 runes are Wick, Tallow and Brine. All 14 are on the runes page.