Random encounters have a 25% chance to become more menacing on approach, stacks up to 4 times. Or that's the gist of it, the idea is that while wearing this mythic it can upgrade the effects from random encounters like the summoner opening a portal calls forth a Daedric Titan, the hunter gets overwhelmed by an elite rabid bear and needs your assistance, the bound traveler has a dozen bandits laying in ambush instead of just 3, or the dueling mages immediately attack you with greater potent spells. It can also affect the mini Daedric Portals that spawn in the overland as well, upgrading the second wave boss to be more powerful or with more minions.
Each player equipped with this mythic item in the surrounding area when the encounter is triggered has a chance of upgrading the encounter, up to a maximum of 4 players.