The lowest monster level found here would be 61, which was 1 level higher than the level 60-cap for player characters in vanilla game. Monsters would increase in power by 1 additional level for every Act, up to level 63 in Act III. At some point, this was changed to level 63 in all Acts. In addition, Life Steal was would be reduced by 80% compared to Normal difficulty. Eventually, this difficulty was removed. Torment is the closest equivalent to it as of 2.0.