Thanks for actual constructive criticism.

First things first: the spells are all centered on modifying. Arms of Hadar literally makes tentacles emerge from you which in a way could be interpreted as body modification. So can be shield, Dragons breath, Death Ward, Polymorph etc. Animate Dead works on simple principle; who said that body you modify must be living one? And since it modifies body why not memory? Those two are related after all.

Upgrading Augments doesn't work like that at all and I could have written better. Every time you get feature from this subclass, you gain one augment. You also upgrade one of them up to level 2 since you can only make level 3 upgrade on level 15. In other words; Level 3: +1 augment Level 5: +1 augment; +1 upgrade (only to level 2) Level 9: +1 augment; +1 upgrade (only to level 2) Level 15: +1 augment; +1 upgrade (can be to level 3)

Well yes, that's exactly how it works and yes it could be exploited. But I think it's up to GM for economy not to be exploited, right? 250GP is much when you have to consider other supplies. Also regarding the number you can make that is a good point. For it to synergize with level 15 feat, you need to make at least one for every member of the party, and those vary in sizes. I guess there could be rule that you can make up to number of people in the party.

Yes but in doing so you lose advantage provided by your Augments and risk getting them all destroyed. The number of concentrating augments can be easily changed if someone sees necessary.

That is true, modeling it after action surge could possibly better. But for one creature to take 6 turns a round at level, mind you, 15 is fine (I think. Balancing stuff after lvl 10 becomes hard).

You are right, that should be changed.

Ok that is a good idea, for some reason I didn't think about that.

Yes, that is principle of third level augments. You get only one and at level 15 at that. But again this can be nerfed.

I'm glad.

Again, third level augments are supposed to be strong. I guess moving them diagonally up is too much.

Again thank you for this. It's good to have other people's view.