Runes are items earned completing Rune Trials. Each can be placed into the Praetor Suit's three Rune Slots, though only one is unlocked by default. Completing more trials unlocks the remaining slots at four and seven trials respectively.
Runes can grant combat bonuses, from increasing item pickup radius to keeping enemies stunned for longer. Any rune can be placed in any slot allowing for customization to suit the player's preferred style.