"Hex" spell is on the city
A character has the Warlock quest "Travel to the city"

Character lands on to the city.

Normally, a character immediately teleports on the Warlock cave. But in this case we have a card without encounter number = priority against every other encounters and simultaneous effect with "land-on" abilities (ex: Druid).

Is this a simultaneous effect? If not, does hex spell have the priority?

"Hex" spell is on the city

A character has the Warlock quest "Travel to the city"

Character lands on to the city.

Normally, a character immediately teleports on the Warlock cave. But in this case we have a card without encounter number = priority against every other encounters and simultaneous effect with "land-on" abilities (ex: Druid).

Is this a simultaneous effect? If not, does hex spell have the priority?

Hex takes priority. The text of Hex states, "Any character landing on the Hex loses a life." So once the character lands there he loses the life, after which he is instantly teleported to the Warlock's Cave.