*little spoiler ahead*
The eye of Tchort... That is looking similary to the eye of Sauron from Lord of the ring.
The creation of Tchort itself is somewhat similar to the creation of the Master in Fallout 1.
Speaking of fallout, the big statue in deep cavern is similar to the vault dweller statue you can find at NCR in fallout 2.
The expansion is heavily inspired on waterworld.
The first quest is nearly about fighting rats, possible reference to the first quest of warrior guild in various Elder scrolls (Oblivion, Morrowind) . Or even a reference to that start in fallout 1, fighting rats in a cavern.
I mean, there is a Lot of references to catch in this game. And even without talking about oddities that a good 1/4 are references.