Taking out enemies in swarms with the void once it grows a bit is really satisfying. It does a great job of selling the increasingly overpowered feeling.
A bit of extra polish, like stronger sound effects or some screen shake when hovering the void over enemies, could make it feel even more impactful. I really liked the particle effects for the blue souls you collect and the ones left behind when enemies die, though it could be a little hard to see them when the void was covering everything.
The enemy models look good even without animations, which is totally understandable for a 3-day jam. Nice work overall!