Who's On Deck? Expanding Wandering Monster Checks

Some months ago I read a post with a brilliant set of tables for converting some wandering monster checks into foreshadowing with lots of details and two stages of foreshadowing. I'll have to hunt it down again to cite it properly.

Here is a simpler rule of thumb approach in the same general direction.

When doing old school wandering monster checks where a six would normally send you to the game's generic wandering monster chart or your dungeon's custom wandering monster table, invert the order of things a bit. Before any action gets going roll twice on your wandering monster tables.
The first roll is to identify who is lurking or hunting nearby. Besides the creatures lairing closest, this monster will be the first responder to noises made, magic emanations, and tracks made by the PCs. The second for a monster or group that has passed this way but is not an active threat. This info is just to prime you so you can think in background about suitable hints and signs, and in the case of the active monster, what's the right moment and approach for a dramatic entry.

When the time comes for a wandering monster check, roll the traditional D6:

4 - the PCs find a sign of the presence that the inactive monster has passed this way or is in the neighborhood. This could be things like tracks, scat, dried blood, dropped possessions, dried up bits of a victim/meal, shed hair or skin, or a faint and distant noise. Initiating tracking on the basis of this sign should be difficult or impossible, but the PCs get some hint of what they might face and maybe tension ratchets up a little. It's probably a red herring if acted on. Reroll now for the next inactive monster to be hinted at the next 4 rolled.

5 - the PCs get fresher and more direct sign, sound, or glimpse of the active monster. A tracker acting on it is likely to be able to track it with normal chances of success.

6 - The active monster attacks or engages with the party. Resolve the encounter as usual. If the PCs are at heightened alertness from a previous 5 roll for this monster, reduce the chances they are surprised. Roll to identify the next active monster when it's convenient.

Since you know the nearest wandering monster in advance, if the right moment to spring it becomes obvious, don't wait for the 6. But in fairness, that probably means skipping the next 6, turning it into a 5.

If going off of general random "could be anything" tables, record the inactive monsters and make it more likely than a completely random check off the table of turning up again, since they now have an instantiated history of having been present. Eventually as this list grows, it can become the list of likely wandering monsters (aside from statically placed ones that go roaming) for the dungeon level. Start using a lead in roll that opts between using the history list and generating a new, completely random monster that gets added to the history, which eventually favors the history list. At first it's 1 in 6 comes off the history list of previous inactive or (survived) active monsters. As the list grows, bump that up, until it is eventually 5 in 6 off the history list, with just the odd newcomer, bumping back down as unique ones get killed off. The history list should probably be seeded at the beginning with the types of monsters that are actually placed. Depending on your realism level, a wandering monster of the same type as a placed monster is that individual, so it potentially already dead or wounded if the PCs visit its lair or another unaccounted for "quantum" individual, so the lair is unaffected.

Pink trail of slime found on a 5.

The rubber band bits were a quick expedient for illustration, but the recent DM Craft video on water gives me an idea for doing various moveable slime trail tokens that should look awesome.