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

Rune · tier 4 · from floor 16

Marrow

Set in a weapon: +14% damage. Set in an off-hand or armour: +45 life.

Play

Drops from floor 16 down.

What it adds

Tier
4
First floor
16
In a weapon
+14% damage
In an off-hand or armour
+45 life
Smith’s price to empty
75 gold

The line counts once per socket it sits in: two Marrow runes in one weapon give twice +14% damage. 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 16, where it first can drop, 1.9% of the runes that drop are Marrow; deeper, the higher tiers join the draw and its share shrinks.

The chance a kill drops Marrow, by floor
FloorsShare of runesBoss killElite killOther kill
16–211.9%1.0%0.12%0.008% (1 in 13,000)
22 and deeper1.9%0.9%0.11%0.008% (1 in 13,250)

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

Inscriptions

Marrow is part of one inscription: Marrowtithe (second of 3, for the Bonecaller). 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 4 rune is Thrum. All 14 are on the runes page.