I only remember this one 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.
The scene in the cartoon you are describing is in “Wizards,” an animated film directed by Ralph Bakshi and released in 1977.
It does not have white haired druid women though.
Heavy Metal has white haired warrior women riding bird things. It has a similar animation style.
I just skipped through the movie - there isn’t a scene that’s somewhat similar described here. Sadly I didn’t find anything else. https://archive.org/details/y2mate.combernievstrumprzlyugsut7q360p
Ugh, you’re right, that wasn’t it. Damn I was so sure.