When you connect, LibreLogin parks you here until you log in or register: only the login and register commands work until you authenticate, then the proxy moves you to the lobby. It is a deliberately bare Paper server on a flat void world with spawn handling, skins, tab list and anticheat, and nothing else. A second lightweight limbo runs on the proxy as a fallback. In normal use you see it for a few seconds. The network also runs a proxy-side whitelist right now, so accounts that are not on the list are refused at login.
The other modes
SkyBlock
Solo, duo, trio or squad islands, each with its own nether and end.
in developmentBedWars
Four maps are built, but the arenas are not set up, so no match can start yet.
playablePrison
Mine, rank up from A to Z, claim your own cell. Three currencies and one boss.
playableCreative
Claim a 64x64 plot, build with unlimited blocks, keep it protected.
playableSurvival
Claim land, build an economy, trade with other players. PvP is on.
playablePvP
1.8-style combat: no attack cooldown, sword blocking, old golden apples.