This is a list of the Known Gates and facts known about gates in my GURPS Dungeon Fantasy: Felltower game.
Gate Spells for DF Felltower
Currently known gates. Teleporters are excluded, as they are not technically gates.
Lost City of D'Abo
Location: Felltower on the level at the bottom of the GFS (Giant Fantastic Stairs)
Destination: The Lost City of D'Abo
Notes: Created Servants can pass through, but ended soon after. Scry Gate revealed a domed room with pictures depicting a wilderness map (?) and a black fortress atop Felltower's mountain.
Unknown Gate #1
Location: Felltower on the level at the bottom of the GFS (Giant Fantastic Stairs), directly opposite the stairs.
Notes: Created Servants cannot seem to interact with it. Scry Gate failed.
Unknown Gate #2
Location: Felltower on the level at the bottom of the GFS (Giant Fantastic Stairs), in an octagonal room.
Notes: Marked with a fool's cap.
Unknown Gate #3 (Nicknamed the "air gate")
Location: Felltower on the level at the bottom of the GFS (Giant Fantastic Stairs), 9' off the ground level at the end of a "landing" sticking out into an egg-shaped area.
Destination: Somewhere in the clouds. PC guesses include heaven, the Sacred Cloud Kingdom, the plane of air elementals
Notes: PCs encountered two air elementals here - on came through the gate after them, another materialized at the gate and met them on the return.
Known facts about gates. Known unknowns are marked as such with details - stated facts are likely to be completely true.
Created Servants can pass through some gates, not others. Currently it's not known why. Thaumatology suggests even autonomous spells can be attenuated over distance and may be affected by time differences - meaning such spells might just end because of distance from the caster.
Wizard Eye spells cannot pass through any gates.
Thaumatology suggests the nature of some gates makes them impenetrable to non-self-willed forces but would allow transport of unliving objects by willing subjects. In other words, magical forces cannot penetrate but people can carry stuff in themselves.
Keys may be needed for some gates; it's unclear how to identify a key. They will not necessarily be magical; the magic may be in the gate which responds to keys not in the key activating a gate.
Gates are definitely known to work intraplanar (same world), interplanar (different world, possible different reality), and it's suggested they may work across time (transport forwards or backwards in time.) Different worlds may not pass time at the same rate as in the world of Felltower and gates may not always transport people instantly from place to place.*
Gates seem to require you to finish entering if you choose to enter - you can't stick a hand in and pull it back out.
* This is partly a meta-game way of dealing with going into a gate on Real World/Game World Day X, finishing the delve and returning on Real World Day X+14 or X+21 without having to do calendar tricks. I can just say, "it's 21 days later, even though it only felt like 3 in that world!"