Honestly... I sincerely dislike this class.
Firstly, of course, it's Psionic Powers are individually discrete spells that you learn and cast same as any other character.
Second, building a class from the ground up to nerf itself back into the ground is not a good design for 5e. When a Wizard runs out of spell slots he can still make decent skill checks and not die from using too much magic. The same cannot be said of this class.
Take a look at 13th level, for example. That's the point where you get 5th Order Powers. That's cool, right? But your dice is only 1d6. So if you roll a 6 you avoid gaining strain. If you roll a 5 you gain 1 strain. If you roll a 4 or lower you gain 5 Strain.
At that level you've got 14 Strain as your maximum. Sure, you could cast that spell, sorry "Manifest that Power" as many times as you roll well and do really good compared to a traditional spellcaster... or you could cast it twice and have your character massively debuffed for the rest of your adventuring day.
Or a third time and die. All based on rolling 1d6 and hoping for a 6.
And what kind of power do you get out of that? Bones of Glass. Give a target Vulnerability (Double Damage) to B/S/P is an example. For 1 round (End of your next turn). And they get a save against it. On a save they take 3d10 Psychic damage.
And you still get 5 points of strain 66% of the time.
Meanwhile a 9th level Wizard can cast Hold Monster and cause every hit on that target to crit (If they fail their saving throw) for up to 1 minute (If they keep failing their saving throw) without gaining disadvantage on all Intelligence Checks until they spend their hit dice to remove the penalty or take a long rest.
In a system that is flipped on it's head, where rather than classes and characters using limited resources they instead take progressive detriments over the course of the day, this class could be 'neat'. But in 5e it stands out as a sore thumb of a class that defeats itself through its core mechanic.
Do not want.
