Operencia: The Stolen Sun

This achievement is for unlocking the third tier from the same tree. There are three tiers within a tree. Not all characters have the same number of skills per tier. For example, a starting warrior only has 1 skill in the first tier of each tree. Each Tier also requires a certain number of skill points be spent before unlocking it. So that same warrior would have to buy 2 of the sub-stat items (circles below the skill) to unlock tier 2.

Your first companion that you get in Lake of Anna, starts with 2 skills in his first tree. When he reaches level 2, spend a point on his sub stat. I chose Intelligence +3, but any of the three will work. This will unlock Tier 2. When he reaches level 3, you will now be able to buy the Tier 2 skill Combustion. By the time he gains two more levels and reaches level 5, you can spend 2 more points on sub stats. This will unlock the third tier in his first tree. This will unlock this achievement.

You do not have to purchase anything in the third tier to get this achievement, just unlock the tier.