Tri's level gauge increases when you mend a rift, and Tri gains new abilities upon leveling up. This page lists the new abilities for each of Tri's levels.

Tri's New Abilities per Level

2. Tri gains a fourth triangle
3. Can hold the Y button to create echoes at a distance
4. Certain monster echoes will require fewer triangles
5. Certain monster echoes will require fewer triangles
6. Tri gains a fifth triangle
7. Certain monster echoes will require fewer triangles
8. Certain monster echoes will require fewer triangles
9. Tri gains a sixth triangle
10. Certain monster echoes will require fewer triangles
11. Certain monster echoes will require fewer triangles