An idea for the dwelling of the SoS!
The home of the Sentinels lays not far from the mouth of Hydra, inset into the sandy cave walls of tunnel P. A yawning overhang creates a large den. The den is more of a side tunnel, smaller than the main tunnel yet it does allow alternate passage under its thick archways. Parts of the rock have been dug out, while others are fortified with stones and pillars to keep the low ceiling stable above the largest Gembound. Years of wind has carved this side-tunnel into a smooth oblong shape. At its lowest and slimmest, it sits at about 8 feet. Along the far wall, farthest from the main tunnel, is a rounded shelf averaging at a foot high that dips and raises when it pleases, often about 3 feet wide. A few shelves atop the first lay further in. These alcoves provide protection from the heated winds blasting from Hydra and a modest privacy if something were to be hung above them.
A large section of the tunnel, easily fitting three or four of the largest Gembounds, shows signs of living and scuffles. The shelf here is at its widest and highest point. It allows for those atop it to look down upon other Sentinels. At its base, dinners and courts are held, and many of the group's meetings occur in this room. A communal water trough runs along the edge of the common room to be filled by apprentices and water mages.
Most apprentices and a few champions sleep in these commons, while older champions and commanders have claimed alcoves for their own purposes. The largest alcove is used, typically, for private meetings and hearings and has an animal hide secured to the wall to separate it from the Sentinels' main grounds.
Inspired by sandstone caves like these. Just.. A large one along Tunnel P.