Mind you, this is going to be a Google+ game, for now, run in Hungarian.
To sum it up:
- an exploration-driven campaign
- XP awarded only for treasure recovered
- extensive use of rumours and quests
- limited number of town activities
- unique magic items (except for potions, scrolls, and wands)
- B/X-esque base + house rules
Rappan Athuk is huge; it has 820 areas described and spread across 48 levels (including sub-levels; although The Bloodways count as only one for being labelled as Level 9D); also, it is pretty deadly. It lends itself naturally to being a place for a cautious exploration-driven campaign, combat only being one of the ways of overcoming obstacles and not a goal of the game. The case being that, I plan to award XP only for treasures recovered - slaying monsters provide nothing in terms of advancement (or rather, it only does so indirectly).
In accordance with the ideas described here and here, I intend to provide rumours and quests to further narrow the focus of the game and provide hooks so that there is always a reason for going into the dungeon. What is more, I intend to reduce the number of activities possible in town to (1) buying equipment, (2) selling loot, (3) identifying magic items, (4) hiring henchmen, (5) gathering rumours, and (6) accepting quests.
Although Rappan Athuk is mostly how I envision a fully written megadungeon, it is far from perfect (and here I am not talking about presentation - although I could); the encounter tables are often uninspired, and the treasures mostly lack atmosphere and uniqueness. Those things I am going to change by rewriting the necessary tables and placing unique magic items and memorable treasure troves (heavily relying on -C's Treasure document and the excellent alternative treasure types by Simon Bull, also published in Fight On! #12).
The rules set we will use is most similar to B/X D&D (Kaland, Harc, Varázslat, a Hungarian clone) with the following changes - thought to be - introduced (once the list is finalised, I will probably summarise the house rules in an other post):
- HP is re-rolled at the beginning of each session
- Target20 combat (1d20 + attacker's to-hit bonuses + defender's AC compared to a static target number of 20) - as I write it down it occurs to me that this is actually already included in KHV
- missile combat is abstracted: ammunition is measured in bundles and quivers, which may deplete after each combat in which arrows were shot (1/d6); volleying provides +2 to-hit bonus but triggers an extra depletion check right away (see Brendan's post)
- silvering a weapon takes 1 week and costs 10 times the weapon's original price; 1/d6 chance to wear off after each attack roll (see Brendan's post)
- -C's On the Non-Player Character will be used to handle social interactions between dungeon denizens and player characters
- encumbrance is handled using a binary stat for each item (objects either count towards encumbrance or they do not); one can carry as many encumbering items as his Strength score (see Brendan's post)