Reactions: Since monsters don't always attack, we need a way to figure out just how they react to adventurers. This is done by rolling 2d6 and finding the result on a table. This table has been slightly altered from the one in OD&D. The original table had just three results: negative reaction, uncertain reaction, and positive reaction. In the Basic Set version, a roll of 2 means the monsters will attack immediately, and a roll of 12 means they will be enthusiastic and offer their help. To be honest, I preferred the original - it was a little more flexible.
The rules for fleeing are partially included. Unintelligent monsters can still be distracted by food, and intelligent ones can be distracted by treasure. But OD&D had a little more complexity to the system, allowing for different degrees of intelligence. But props to Holmes for getting the basic ideas in.
Experience Points and Levels: The Basic Set uses the experience point system that was introduced in Supplement I. So while you still get one experience point for every gold piece worth of treasure found, monsters killed are worth much less than they were in OD&D.
I'm intrigued to see that treasure XP is awarded based on how the treasure is split. So, if one guy takes 500gp of the treasure and another guy takes 200, the first one gets a lot more XP. This even applies to rat bastard PCs who steal from their buddies. This is something that honestly never occurred to me, but then again our groups were sticklers for splitting the treasure evenly. It's something that never came up.
The chart for calculating monster XP is the same as that from Supplement I, with the sole exception that monsters under 1 Hit Die are lumped into one category, instead of split between ½ and 1-1.
The rule that characters killing weaker monsters receive a commensurately smaller amount of XP is retained. This gets me to wondering just how this is calculated when you have a party with a disparate level range. If Bob is 5th, Jim is 8th and Steve is 2nd level, how do you figure out the percentage? Do you take the average? Or does each character get a separate total based on his level alone?
Oh, and you still can't advance more than one level at a time.
Thief Abilities: No changes here: everything is still rolled on percentile dice, and you only get one try. The only thing of note is a new NPC, Drego the 1st level Thief. Always nice to have another fellow I can add to the Adventurers' Guild roster.
Clerical Abilities: Hey, Turning Undead gets an actual explanation! The rules are identical to those presented in OD&D in content, but in presentation they’re a lot clearer. And it helps greatly to be told just what happens when a monster is turned. OD&D was rather vague on the matter.
Magic Spells: This section gives an overview on spell-casting, and draws together a bunch of info from different sources, particularly some of Gary's articles from The Dragon. The requirement for magic-users to speak and gesture is one such bit of info, meaning that they are now specifically unable to cast while bound and gagged. Material components are also mentioned. Casting while walking or running is forbidden, as is casting while in melee. All of this stuff had been talked about previously, but this is the first time it appears in the core rules.
Magic-Users are forbidden from taking their spell books into the dungeon, but they can still create scrolls as per OD&D, and also research new magic.
The effect of Intelligence on spell-casting is brought in from Supplement I. So Magic-Users still have only a certain chance to be able to learn any spell, and also have a limit on the number of spells they can know. The table used hasn't been changed at all.
Malchor, a magic-user previously mentioned and brought into my campaign as an NPC, appears again. This time we learn that the poor bugger only has an Intelligence of 10.
The info as presented seems to apply solely to Magic-Users, not Clerics. In OD&D Clerics used spell books just like Magic-Users, but it seems that from this point on that's no longer the case.
Saving Throws: Nothing changes here, but it is noted that the undead are immune to poisons and spells that require a living mind. Oh, and zombies are apparently poisoned by salt. I suppose there's a mythological precedent for this? I kind of like it. (A bit of further research reveals that in voodoo, zombies that are made to taste salt will return to their graves, so it's a nice bit of work there from Mr. Holmes.)