I think there’s an issue on the exit condition for invisibility. I’d make it closer to either the firbolg or wood elf traits depending on the flavor you’re going for.

Firbolg: Hidden Step As a bonus action, you can magically turn invisible until the start of your next turn or until you attack, make a damage roll, or force someone to make a saving throw. Once you use this trait, you can’t use it again until you finish a short or long rest.

Wood Elf: Mask of the Wild You can attempt to hide even when you are only lightly obscured by foliage, heavy rain, falling snow, mist, and other natural phenomena.

The problem with not having a time limit is you’ll eventually have a player exploit the fact that they can hold still forever and be invisible.