My formative CRPG experiences were the Pokémon series and TES IV: Oblivion. The former needs no introduction, but the latter is somewhat of the black sheep of the Elder Scrolls family, lacking both the mainstream success of its sequel, Skyrim, and the cult status of its predecessor, Morrowind. To me, however, it was just about the coolest game I’d ever played up to that point. My Altmer Wizard was my favorite ever game character to play, and I cleared out about every necromancer dungeon and Oblivion gate on my quest to become Archmage and Champion of Cyrodiil.
One of Oblivion’s most maligned features was its use of level scaling - that is to say, challenges scaled to the level of the player. An Oblivion gate at level 1 will contain weak dædra such as scamps and dremora churls, but at level 20 will contain strong dædra such as Spider Dædra and Storm Atronachs. Compare this to, say, Fallout: New Vegas, where merely taking the wrong path can lead you into Deathclaws you are woefully unprepared to fight without power armor and an anti-material rifle. While yes, these lists can make the game seem homogenous (and lead to absurdities like common bandits using rare glass armor & elvish weaponry), they are great at stocking dungeons with a common theme. You know you’re in a necromancer dungeon when you meet the skeleton guards; and further on you know you’ll meet zombies, ghosts, wraiths, and maybe the lich that is master of this place…
With the joyous simplicity of OSR (monsters are a short stat block + a special ability) or FKR (monsters are descriptive, worlds not rules!) these levelled lists can be rescued from the scrap-heap and given new life. They streamline dungeon stocking by sticking to recognizable themes rather than reams of specific monsters, and replace the bizarre and contradictory wandering monster table with something you can theme to your dungeon.
Roll or choose once for theme, and roll or choose once for threat level. Some examples below!
These are just examples. You could easily expand it out to a d66 table with specific examples of monsters, for a level-less game, but I think the freeform aspects of this make it both a useful tool and a good basis for referee improv - something I think should be encouraged!