Andi Green spotted a little known secret tucked away in Ultima Underworld: The Stygian Abyss. A set of runes includes a defiant Kilrathi message from the future! "Thou canst not defeat the Drakhri!" The old-timey English was obviously reworded slightly, but Drakhai (Kilrathi Imperial Guards) ended up becoming Drakhri (medium fighter). Both emerged about the same time (the Drakhai in SM2, Drakhri a few months later in WC2), but they're definitely not the same thing!
There's the pessimistic reference to Wing Commander II deep in the Stygian Abyss.
While Origin was working hard on Wing Commander 2, a separate team was developing the original Ultima Underworld title to be "the first continuous-movement, 3D-dungeon, action fantasy." Both games were actually rereleased on a special combo disc to cross-promote the series in the early days of CD-ROM. The Stygian Abyss managed to make it out the door before first person competitor Wolfenstein 3D, and the group behind it would later go on to produce System Shock.