The major differences between DragonQuest 2nd Edition and 3rd Edition are in the magic section. Chapters 46 & 47 (Colleges of Black Magics and Greater Summonings) were removed as were rules 43.7 (The Ritual of Binding Earth) and 54.3 (The Seduction Ability of Courtesans). Chapters 46 (The College of Summonings), 47 (The College of Shapings), 48 (The College of Rune Magics), 49 (Notes on Magic), 50 (Creating New Colleges), and 51 (Guide to Herbal Lore) were added.
There were also significant tweaks to many of the spells, in some instances starting them with a negative base chance of succeeding, all but assuring that even attempting the spell would cause backfires.
Some other minor changes were made with regard to racial adjustments and the wording of "evil" spells/abilities. A couple of typos in the weapons chart were also fixed, so that to wield a giant glaive it was fixed so that it was actually a requirement to be of gigantic strength.