Terminology

Foils
The Undertale selves that Chara faces are the "foils" to their canon-verses.

"[...] a character that has characteristics that oppose another character, usually the protagonist. The foil character may be completely opposite to the protagonist, or very similar with one key difference.” (literary definition)

Foilverse - Setting
It looks the same as in the Undertale game, but has a slight haze in the air and overall grimmer look. The water looks glossy, like liquid mercury, and Chara can see Frisk on the other side if they peer into it. A heavy, gloomy feeling looms about and the inhabitants seem to have all but given up hope.

For specific locations, click here.

H.O.P.E.
lit.  H aving  O ptimism and  P ersevering through  E verything