If they are outside of Gehennom, Infidels’ prayers to Moloch are more likely to succeed the deeper they are in the dungeon.

Player monsters who spawn at a certain depth have a very low chance of generating carrying their quest’s artifact. This chance is highest when deeper than the Castle, but is still low.

Fort Ludios has a constant level difficulty, of perhaps 20, not varying based on where the game internally decided to place its floating branch.

A new branch with infinite levels, whose level difficulty continues steadily increasing the deeper you go. Monsters killed do not drop anything, except that there is a very small chance, increasing with greater difficulty, of dropping a single wand of wishing. Unlike the rest of the dungeon, monster generation cares only about the level difficulty, ignoring the player’s experience level.

Levels in this branch are non-persistent. To prevent destroying any unique items, you either can’t bring them into the branch at all, or you are prevented from leaving a level in any way while they are on the level somewhere other than your person. Not determined what drinking a cursed potion of gain level would do.

One way to increase the challenge and prevent the hero from resting on the downstairs every level and starting each new level fresh is to suppress or remove natural HP regeneration in this branch.

Using an upstairs will take you back to the branch entrance, which may then close off forever. Possibly, 9/10 of upstairs will just crumble to nothing upon arrival in the level (whether this 9/10 is random or happens regularly every 10 levels isn’t determined). This makes it less easy to decide to bail out, though levelport or branchport would probably still work as escape items.

Not determined is to what degree the branch should enforce the player to spend time on each level. The three proposed options are:

1. No enforcement. The player can go as deep as they want by digging a hole right away with the increased risk it entails.
2. Enforced finding the downstairs. The floor is nondiggable, so the player has to at least reach the downstairs in order to travel further.
3. Enforced battling a certain amount (or all) of the monsters. The downstairs will not let you travel down them unless you have killed a certain amount of monsters on the level.

Vaults on deeper levels have walls that take multiple digging actions to dig through, like shop walls do.

Fix the effective level difficulty of all Sokoban levels to either the level past the one with the stairs, or the level with the stairs, or a constant 9.

It’s a common refrain that Sokoban was too easy in 3.4.3 with its easier difficulty as you progress through it, and that it was too hard in 3.6 with its harder difficulty. Fixing it at a constant difficulty is a popular middle ground.

Occasionally, when a bones file would create a ghost (e.g. most times), and the level difficulty is high enough, create a wraith of the player instead. If in Gehennom, occasionally create a shade of the player.