Scion/6th

Intuition

By 6th level, you gain a strong intuitive understanding of a certain kind of creature—your affinity—as detailed under your progenitor features. You become better able to understand the minds, the motives, and the physicality of these creatures. You are an expert on every Intelligence, Wisdom, and Charisma check made about or against creatures of this type.

Being an expert lets you add a bonus die to applicable ability checks. The size of the die depends on your proficiency bonus. A +3 bonus grants a d6, +4 grants d8, +5 grants d10, and +6 grants d12.