The Infinity Engine by BioWare is synonymous with great RPGs. You think Infinity Engine, you think Planescape: Torment, or Baldur’s Gate. Or Icewind Dale. All great level-grinding adventures and all published by Interplay in the late ’90s and early 2000s.
The Black Pits II: Gladiators of Thay is an arena combat-based add-on for the Baldur’s Gate II series, given away free with the Enhanced Edition in 2013.