Ah, the current text reads: "the invisibility lasts until the end of your turn", not next turn. This was the source of my confusion. That clears everything up!

Thank you again for all this work. One of the very cool things about your rules is the ability to mix-and-match abilities without too much fear of throwing off the balance. For example, one of my players is a warlock whose patron is a hybrid fey-shadow to suit the in-game story (shadow spells, shadow abilities at levels 6, 14, fey for all the rest). I know your rules aren't explicitly designed for this kind of hacking, but that flexibility is great for aligning the mechanical side with the story.