Against a wall is a semi-circular pool. There are other pools like it throughout the dungeon. If a character pours water from one pool into a second pool, that character may teleport freely from either pool to the other from then on. This is Pool #1.
The twin dragons Mardulopennum and Vergilotolabathar. They are fire-breathing dragons of the youngest age category, barely a year old. They are keenly aware of their vulnerability and willing to have conversation with PCs.
Both are able to speak.
Mardulopennum can cast the spell Sleep once per day. She is inclined to arrange the death of PCs – whether through direct attack, trickery, or timely betrayal – if she suspects they will be a threat to her or her brother.
Vergilotolabathar can cast the spell Charm Person once per day. He is most interested in building the twins' horde. He may suggest teaming up with the party against a stronger monster he believes has prime treasure (and he is correct in choosing treasure-rich targets 90% of the time). He may also betray the party if they have particularly choice treasure on their person – powerful magic items or lots of loot on their way out of the dungeon, for example. He will become very loyal for 3d4 months if the party gives him valuable treasure – a choice magic item or over 1000 gp – and resist any attempts by his sister to kill the party.
Neither dragon is stupid or evil for the sake of evil. If they betray or attack the party it will be when they have maximal advantage – unless they are defending themselves in desperation.