Rune Cage is a skill located in the Dark Magic (which can be found in the Sorcerer skill tree). Rune Cage is a morph of Rune Prison.
Rune Cage deals the following types of damage: Magic Damage. Which means that it gets buffed by the following blue champion point trees: Elemental Expert, Elf Born, Master at Arms, Spell Erosion. Also the following red champion point trees protect against this skill: Elemental Defender, Iron Clad.