(this is just my interpretation/headcanons)

Voids
Empty, infinite spaces found between universes. Difficult to access and even more to escape. These are usually defined by having no measurable limit and completely empty apart from interference from other entities. Voids usually contain nothing and can be any colour, though they're usually black or white. You can only enter a void if you either know where to go and have the ability to do so or stumble in between the fabrics of space-time. It's highly recommended you know how to exit a void and have the power to do so, else you'll be stuck and the chances of someone finding you is not impossible, but very low.

Sometimes, they're are 'voids' that don't follow the definition of a void. These are called 'false voids', yet they're very alike to normal voids that they're often perceived as normal voids as well. False voids may have a reachable limit, looped spaces instead of carrying on forever or have something existing in it already. Accessibility may vary from entering and exiting with ease to as difficult as a normal void. Another factor is that false voids can be created by anyone and anything, by any entities, whereas normal voids just sort of.. spawn, for lack of a better term.

If you get stuck in a void, false or not, it would suck. What would suck more is if you start changing. If you're trapped in a void for too long, your physical, mental and emotional state can change, for better or worse. This is known as 'the Voiding Effect', and both voids and false voids can have this effect. Changes can range from a colour shift in your appearance to completely distorting your body and sanity. Some voids' Voiding Effect can happen in an instant or worsen over time the longer you're stuck. In most cases, the Effect will remain even if you're out of the void. You're memory often deteriorates as well. Some think it's a way of the void 'claiming' an entity, detaching them from their original universe and have them remain in the void.