chalk(n)
common meaning: something teachers use to write on a blackboard.
uncommon meaning: a kind of soil called "bai e".

They wander like specters on the fringes of the Dreamscape, carefully concealing their emotions and avoiding memories that smell sour or bitter.

There are two words worth mentioning in this sentence.

1.specter

common meaning: sth unpleasant that people are afraid might happen in the future

uncommon ones: a ghost

2.fringe

common meaning: the front part of sb’s hair that is cut so that it hangs over their

uncommon meaning: the outer edge of an area or a group

keen (adj.)

common meaning: 

①wanting to do sth or wanting sth to happen very much

②quick to understand

uncommon meaning: highly developed (senses) , for example: Dog has a keen sense of smell.