Just my cranky opinion.
#1 The cleric class.Cleric spells are fine but Van Helsing and turn undead belong in Hammer horror films and activist deities belong in Greek Myth. My D&D can do without them.
#2 Alignment. Just say no to objective morality and know alignment and maybe even detect evil, especially if it works on people. However if you must have alignment factions the old school Law/Neutral/Chaos axis is about as much as you need. Law for Cities and Order, Neutral for just getting along and Chaos for Caprice and Disorder.
and # 1/2 The Thief. Old School Games do need some means of adjudicating common adventuring tasks like opening locks and climbing walls. Whether its wall climbing Cimmerians or Burrahobbits they are very much part of the cannon. And while I don't mind a class that focuses on that sort of thing these abilities do not need to be exclusive class powers. After all anyone can sneak, hide, backstab or climb even a stodgy old wizard.
A note on my Spider Cult of Mirkwood Campaign posts - As you may have noticed, I’ve posted a lot about this campaign over the past day or so. The reason: my *Adventures in Middle-earth* campaign is starting up...
4 weeks ago