Fantasy book series with non-human races and labyrinth

Question

I'm trying to identify fantasy book series I encountered some time ago. Here are things I remember:

• it was a fantasy setting but with some s-f elements; with many worlds and possibility to travel between them; resembling Planescape setting a little,
• the two main races were non-human and probably hostile to each other,
• a labyrinth (?), which somehow played an important role in the plot,
• a protagonist was some kind of emissary and was sent on a mission to another worlds
• time period: 80s - 90s

Does anyone know what it is the name of the series?

Answer 1

The Death Gate Cycle is a series of seven fantasy novels by Margaret Weis and Tracy Hickman that involves planar travel and contains quite a few sci-elements. The books were released between 1990 and 1994.

The series features:

• Travel between multiple elemental planes of existence: the Plane of Fire, Plane of Earth, Plane of Air, Plane of Water.
• The the Sartan and the Patryns, two godlike races, are locked in a war to control the other, "lesser" races (Dwarves, elves and humans).
• The Labyrinth is a prison world that figures largely into the Sartan/Patryn conflict. Spoiler alert:

  The Patryn are imprisoned there.

• One of the main characters is Haplo, a agent of the Patryn who travels among the Elemental worlds at his master's request.

Answer 2

Possibly some of the books in the Riftwar cycle by Raymond Feist?

• multiple worlds with different ways of access through portals
• Non-human races - Elves, serpent people, Valheru. At the beginning of the series the main race is human, but many of the major characters are not human.
• Pug (aka Milamber), the main character of most of the original books, travels back and forth to many of these worlds in various roles, from slave to emissary to ambassador.
• Some parts of the stories take place in caves and labyrinth-like "between worlds" places
• the series ran from 1982 to at least 2000.