FINAL EDIT: @nomad@infosec.pub found it, it’s Roswell Conspiracies, thank you everyone!
The white-haired females would frequently meet at a Stonehenge-like monument where there was also some kind of a portal. I also only remember this one specific scene and nothing beyond that:
(a bit graphic, click to show)
There are men who are restrained, and their mouths are being held open. An elderly man places a large egg on top of a ramp, and the lower end of the ramp is connected to the mouth of one of the restrained men. The egg eventually hatches, and a big snail emerges from it. The snail then slowly slides down the ramp and enters the mouth of the man, who is forced to swallow it. As a result, the man is immediately brainwashed and gains additional physical powers and will serve as an additional soldier for that old man.
EDIT: the art style resembled that of X-Men Evolution
It was certainly a cartoon and the art style resembled that of X-Men Evolution (btw I just went through the 4 seasons and it doesn’t have a coven of white-haired druids or the snail scene so it’s obviously not it).
You could try looking up the work of people who worked on that show, if it’s the same style it very well could have some of the same artists, directors, etc.