Tomas will probably be the one to catch anything mysterious, but she can still poke around with him, and Lhín might actually spot something.

Tomas searches the room. "No traps or secret doors. All the drawers are empty. There's nothing of value here, other than the room itself."

Lhín's blindsight finds nothing the others haven't already found.

"Onwards?" Julen again will be their leader.

Julen leads them into the next room.

The erotic frescos in this domed chamber have faded, but their intent to inflame the passions of those occupying the room is still plain. Four marble benches sit against the walls and a complex mosaic of thousands of colored chips form a huge starburst on the floor.

Tomas scans the room quickly. "The mosaic is a magic item."

Detect Magic. Can she tell anything about what it's doing?

The mosaic emits a strong enchantment aura. She doesn't know anything else about its functions.

Tomas studies it for a few moments. "I don't know what it does."

"Nor I, but that is a strong aura. Whatever it does, it does forcefully."

"Right. Let's walk around it. Can you spot anything else, Tomas?"

He scans the room. "No traps or secret doors, as far as I can tell. The murals are... uh.... did the Thassilonians really perform complex alchemical experiments while having sex? Is that a thing people actually do?"

"It does seem a poor decision, though I suppose it is said the Thassilonians harnessed their vices somehow. Onwards?"

Julen leads them around the mosaic and into the next room.

A simple pool of pure, clear water fills the central area of this room. It's covered by a brass grate. Doors lead out of the room in all four cardinal directions.

Tomas scans the room. "The pool of water is a magic item." 

And they knew this area existed because there was water flowing in this direction...

"I suspect this is the endpoint of the wall crack. The water must be flowing both in and out, if so, unless it simply vanishes." Does Lhín see the water flowing in either direction? And Detect Magic, while she's examining things.

The pool of water has a strong abjuration aura. Nothing else stands out.

Lhín can sense the water flowing upward from a tunnel below the pool. It somehow doesn't ever seem to end up outside the pool.

"Abjuration, strong, and possibly something subtler to keep the water in the pool under that. Defensive enchantments here seem strange, given the grating. Most likely not a trap. Protective enchantments of some sort, with the grating to make them more difficult to use? That makes little sense."

Can she see anything about the magic's functionality? It's too strong for her to have much hope, but there's no reason not to try.

She cannot discern anything about the magic pool's functionality.

Tomas studies the pool intently for a few moments. "It casts greater dispel magic on anything that touches the water. It doesn't use charges or have limited uses per day. The only other item with a similar effect I'm aware of is a holy avenger wielded by a paladin. We're definitely in the lair of an archmage, to find something like this."

"That seems incredibly valuable, though not immediately useful to us. Does it require submersion, or is mere contact sufficient?"

"Submersion. I'm not sure it can be moved. The magic is worked into the space, similar to the bedrooms."

"Seems too expensive for the recipe to be worthwhile even if we had it, at a guess. We may wish to remove the grate for easier access if we need it in the future?" And by we she means Julen here, as her gaze makes clear.