Ori has three different skill trees that you can upgrade using ability points earned from ability orbs. Everything you kill increases your ability orbs and once the yellow circular bar in the bottom center of the screen (Between Energy and Life) fills up you gain a point that can be spent on a skill. The Utility Tree is the central of the three upgrade trees, all the early skills cost only one point while a few of the later ones require 2 and the final skill takes 3 points to purchase. Once you buy the final skill which gives you the ability to see Secret Areas this achievement unlocks.