The thief, as we have stated before, is a bit of a tricky one. I honestly like the class, but can well understand why many in the 'old school renaissance' no longer allow the class in their games. I, however, really want to try and make it a viable choice (I'd also like to do that for the fighter as well, but one thing at a time...) and so I'm going to throw out a couple of ideas.
1) Point buy percentages. This sort of thing, presented in 2nd Ed. AD&D, has the advantage of allowing the player to be really good at, at the least, one thief ability. The downside: Over-specialization and I don't really care for it.
2) Ditching the normal (to AD&D) bonuses due to a high dexterity and replacing that with a flat bonus to all thief abilities equal to the thief's dexterity score.
This doesn't address the issue that some have brought, i.e.: the thief is an unneeded class as the player should be challenged, not the character, but, though I find the idea attractive, I do think the character's abilities should be taken into account...
[New Magic Item] Dragontooth Necklace - Dragontooth Necklace The bandit bound the gnome’s hands securely with rope, then the hands of the elf and druid. He turned to tell the outlaw leader, shrug...
1 day ago