Confirmed — and thank you for flagging it as critical, because teleporting UP is currently a guaranteed no-op.

After a teleport the code looks for ground under the destination and settles you on it if it's "close enough". The trouble is that "close enough" was set to the teleport's own range (150 for the GM teleport). Teleport up 150 and the destination feet sit 150 above the floor you're standing on — which means that floor is *exactly* at the tolerance, wins the search, and you get yanked straight back down to where you started. In a stacked shaft like Eos Tower 100th Floor that's every single attempt, so it reads as "teleport refuses to put me anywhere I can reach".

The fix is to make the snap what it was always meant to be — a short landing tolerance (30px, the same one portal arrival uses), not the whole travel distance. Then: teleport up onto a ledge whose surface is just under your new feet and you land on it; teleport up into open air and you actually rise and then fall, instead of never moving.

Confirmed and fixed. Teleporting upward was doing literally nothing. The landing check was allowed to snap you onto any floor within the skill's whole range (150px for the GM version), and the floor it finds by searching downward from where you were heading is the one you were already standing on — exactly 150px away — so it passed the check by a hair and yanked you straight back to your starting spot. The snap window is now 30px, the same one portal arrival uses. So you settle onto a ledge you arrive next to, and if there's nothing there you arrive in the air and fall, instead of being rubber-banded home. Left/right teleports across a gap now also just drop you rather than being pulled down onto whatever distant floor happened to be within range.