From Edge of Darkness Wiki
Summoners p. 186
A minority of mages Awaken with a quiescent connection to other realms, which, if developed, shows itself as an inherent talent for summoning magics. On a level far below conscious thought, the mage has an instinct for the rules that govern other realities. Awakened scholars refer to this gift (or curse, if you like) as a Summoner’s Soul. Every mage with a Summoner’s Soul is mystically inclined towards one realm over the others, while still being more naturally adept with summoning magic in general than most mages. A player should choose the realm to which her character is linked when selecting this Merit. A mage tied to a Supernal Realm in this manner must select his Path Realm; this inborn connection is probably what drew such a willworker to his particular Watchtower in the ﬁrst place. When spending Willpower on a summoning spell attuned to entities from his character’s favored realm, the player of a mage with a Summoner’s Soul receives ﬁve bonus dice, or four bonus dice with respect to summoning spells that call upon other realms. When dealing with entities from his favored realm, all of the willworker’s Social Skill rolls receive two bonus dice as a result of this special bond. But this may only be selected at character creation or with Storyteller approval.