Gates (Hypogeum)

[Portals don't get an art]

Gates are sort of a black box. They are found, occasionally, in the Hypogeum. They look like glowy bits of vaguely circular 2d geometry about the size of a person. They can appear when you solve a puzzle or get to the end of a dungeon. Most of the time they, at least one of the gates appear nearby the thing that "caused" them. Sometimes they don't, though. People near the gate when it opens sometimes report hearing a sound, but accounts vary (sometimes like the tinkle of a bell, sometimes a "VOOM", different people hear the same gate opening different ways). They don't appear to be made out of Stuff, and they aren't affected by magic. If you break a wall around a gate, the gate stays there.

Almost all gates are blue. 

Gates, as was implied, usually come in pairs of two. Going in one gate brings you out the other. Simple. Gates are permanent. No one has ever reported a gate closing, at least. Gates always go both ways. This is not always useful. You can't be halfway in a gate. Going into it at all brings you out the other. Nobody knows what constitutes matter gates transport. It almost always includes people and creatures (including living plants), but sometimes doesn't include things like clothes, while other times you can push a wheelbarrow through. Smart travellers wear weavemoss underwear.

Gates usually transport you a fair distance. People report gates that they open usually bring them to somewhere the want or need to be. Definitely not always true, but it is significant. Other "favorites" of gates seem to be local landmarks and places so far away nobody's ever heard of them, except maybe in legend. If gates were truly random, as some claim, it should almost always transport you very far away, since there is a lot more of "far away" than "close". So they probably aren't exactly random. Also, gates that transport you far away apparently tend to be "temporary one-ways". That is, they'll drop you non-lethally from a high up platform that is difficult to ascend to, or release you in a lake so deep you barely make it to the top, or exit into a structure that locks as soon as you walk out.

You shouldn't go into a gate if the geometry isn't perfectly two dimensional, and you shouldn't go through a gate that isn't blue. Or at least, so they say.

[I don't like this prompt]