A mal rune is a mid tier rune that can be socketed into armor and weapons. You can cube 2 um runes and a topaz together to get a mal rune. You can also obtain a mal rune from hell countess. You can get a mal rune from the hell hellforge quest.
A mal rune requires level 49 to use.
Horadric cube recipes with mal runes
transmute 2 mal runes and an amethyst to create an ist rune