Ori and the Blind Forest: Definitive Edition - Nintendo Switch

There are a total of 33 Ability Cells around the world. Added to the experience you get from killing enemies, this should just be enough by the end of the game on Easy or Normal to unlock every ability tree upgrade and get Phenom (as well as Soul Master, Utility Master, and Combat Master). I do not advise going for these four achievements on Hard mode because it takes 75 ability upgrades to max out tree on hard, as opposed to only 54 upgrades on Easy or Normal.

The video below shows all collectibles in the game, including all 33 of the Ability cells to make netting these upgrade achievements easier.