Do I always think of game mechanics = traversal verbs? Do I always have to have a character?
SITUATION OF INTEREST - sunlight hurts, moonlight heals.
MECHANIC TO OVERCOME - wing-bashing open portholes to make and break shelters, inspired by the idea of how a typical vampire would've had to survive its first days.
AVATAR FROM FANTASY - rising from an initially tattered, yet spry set of moth-like wings to an elegant, powerful form of movement with VFX trailing behind you when you soar through shade and the night sky.
WISHLISTED GOALS
Encountering other people who likewise become a light-wielding threat, but also a resource to consume or infect.
Flying up/down great changes over the world's elevations.