From a user called "Courts88" at
http://www.chaptercheats.com/cheat/pc/110867/Baldurs-Gate-En...Easy "Loremaster" Achievement Guide
A regular bard is required. The Lore skill is based on character level, Intelligence, and Wisdom. At level 8, a bard with 18 Intelligence and 18 Wisdom will reach a 100 Lore skill.