Runes

Runes are special items earned by completing Rune Trials. Each rune can be equipped and placed into one of 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.

There are twelve total Runes that can be found and unlocked through the course of the campaign. You will be able to find roughly two Rune Trials per general level starting with the Argent Facility and onward through the campaign until you reach the Lazarus Labs, which contain the final two trials and runes.

Like weapons and weapon mods, Runes can also be mastered to provide greater benefits.

Trivia
Runa (Doom4)
 * Saving Throw comes from the Dungeons and Dragons roleplaying game, which often makes players roll dice to have their characters avoid a harmful magical effect or save themselves from a dungeon trap.
 * A few of the runes could possibly be references to famous songs. The Dazed and Confused rune could be named after the Led Zeppelin song of the same name. The same is true with the rune named Seek And Destroy, which probably is a reference to the Metallica song of the same name.