This being a classic D&D hack, I went with the traditional six abilities of course. For their description, I mainly cribbed from Old-School Essentials. I also added a note to each about which things it modifies. I won’t enumerate those here because we’ll get to those individually when I discuss other parts of Hackbut. Suffice to say that I am largely sticking to B/X here.
Speaking of modifiers, I did choose to diverge from OD&D and B/X for their values. OD&D via S&W has a diversity of modifiers across abilities, which I find unwieldy. B/X has that +/-3 at the extremes which feels a bit much when used as a generic modifier with my previously discussed approach to ability checks. Instead I’ve gone with Delta’s rationalized range of modifiers: 18-16 +2; 15-13 +1; 12-9 0; 8-6 -1; 5-3 -2. Nice and clean and if necessary easily repeatable in both directions (increase by 1 for every three points).
I guess the final thing to remark upon is experience modifiers for prime abilities. Here I follow Ynas Midgard’s approach in KéK, which I found quite clever. In a response to a comment of mine he explains how prime abilities modify the experience required for the next level, in stead of XP received. This eliminates the need for repeat calculations each time XP is received. Smart. The XP modifiers follow the same segments as the ability modifiers: 90%, 95%, 100%, 110%, 120%.
That’s about all I have to say about abilities. Pretty straightforward, as can be expected from a thoroughly vanilla classic D&D hack.