A VeNaToR is actually a a typ of troops for the tyranides in the tabletop game "warhammer 40k". It is also someone who changes his mood every day (while it mainly stays depressed).
You will find these guys talking on any community discord servers. They are original from Pakistan and only play Minecraft as a game and use discord a lot.
When something is deemed voluntary, yet necessary. Thus, it could technically be thought of as mandatory despite being voluntary.
Person 1: "Man, college is going to bite me in the ass. Maybe I just shouldn't attend."
Person 2: "Yeah, college is vandatory like that."
Person 1: "What do you mean by that?"
Person 2: "Well you don't have to go to college, but good luck with life if you don't."