MagisterCultuum
Great Sage
The spell is Trust, the third level spirit spell. It actually works though a Feat and can only be used once per player per game (and allows it to show the custom "You Seem Trustworthy" reason rather than the generic "Past Events..."), but making a repeatable spell that improves relations would not be difficult.
p.s. It really seems like would fit better a Shadow spell, especially since Esus was the Angel of Trust.
p.s. It really seems like would fit better a Shadow spell, especially since Esus was the Angel of Trust.