Hell Levels
Inspired by a conversation with Cascade Default
Caveat Emptor
This is a change designed to slow down advancement. Not every table wants that kind of slowdown which is understandable.
Hell Levels
This is intended to be used with your favorite version of D&D. A "Hell Level" is a character level where their XP rate is reduced by a percentage to prolong their time at said level.
The standard place to put hell levels would be 4->5 and 8->9. These break points represent large spurts in power for the average Classic D&D character.
The level from 4->5 is reduced by half. eg 2000xp would be reduced to 1000xp.
The level from 8->9 is reduced by a quarter. eg 2000xp would be reduced to 500xp.
This penalty is applied after all other xp adjustments.
Why?
It lets the game and those characters experience the full breadth of that tier of play before they blow through it so quickly. It also provides places where new PCs and other late joins have some time to catch up to other PCs that have been alive longer. With other changes to xp gain such as giving the full amount not divided by level, this change lessens the blow of having to catch a character up to the rest of the party.
Other benefits would be an ability to dot even more treasure around your dungeons and wilderness hexes without worry of it ballooning to ridiculous amounts.
With some editions adjusting xp by race and prime requisite you can adjust those numbers to make "speedy levelers" or "slow levelers" which gives another lever to adjust to taste.
Worked Example
Level limited games are becoming increasingly popular. My next D&D will likely lock PC level to 3, but now if I make each level after 3 a Hell Level the power and capability of the PCs will still be relatively flat but longstanding characters may get to level 4 or level 5.
Anyways, be well and go work for that level up!