Based on details in the 3.5E supplement Serpent Kingdoms, this is my combat map interpretation of the portal sanctum in the Scaled Halls of Varae under the Cathedral of Emerald Scales in Hlondeth. The portal leads to the identical Pit of Vipers in Ss'inthee'ssaree on the Lapal Sea, and fully activates 5 rounds after any creature sets foot on it, and any creature on the dais when it activates is teleported.

I imagine one rune in the summoning circle activating at Initiative 20 every round. It creates a hard deadline to either get the BBEG with the McGuffin away from the portal at the right moment, or get to it at the right time to teleport with them. The centerpiece with scorch marks is supposed to be where somebody teleporting to here from there would arrive, because otherwise there was a very big empty space in the map that I didn't like.

The trees are meant to emulate the Black Jungles around the Lapal Sea, as generally noted about Hlondeth in Serpent Kingdoms and The Vilhon Reach (2E supplement).

The pillars and multi-story look were just something I wanted to try after seeing some of Mati's creations. They're created using bowsprits, setting the blend mode to luminosity, and painting behind them with a gray texture brush -- it's as tedious as it sounds, but the I think the result is an interesting multi-tiered map.

The shadows on the stairs, I found out, could only be applied if I flattened the stairs to the background, which is annoying since there are other stair assets that do have shadows.

The second level would have doors to some undetermined number of undetermined types of rooms.

The magical lights from the skulls are to give the place some sort of illumination, since this temple is basically in catacombs 200 feet underground. I imagine them activating as part of the teleportation ritual., and not being very luminous. This is a combat map, though, so I felt I needed something to indicate that the room isn't as bright to PCs as it looks to players.