The Speech Pack was an enhancement for the floppy disc version of Ultima VIII: Pagan.
Originally, Ultima VIII included a limited amount of spoken dialogue; however, due to size constraints, this speech was not included on the floppy disc version of the game. A disc that included this spoken dialogue called the "Speech Pack" was sold separately by Origin; however, because it was expensive and added little to the game, it sold poorly.
The CD-ROM version of Ultima VIII came with speech already, and wasn't significantly more expensive than the floppy disc version, making the Speech Pack's value even more questionable.
The Speech Pack adds voices to the Titans, Zealan Gods, Khumash-Gor and rest of the Guardian voices past the intro movie.