D&D 5E How I prep monsters in 5E D&D.

[^Dagon^]

I came back and found this thread because I have been at it again, most recently with

1. Will o' Wisp (wow, so different from earlier editions and now undead? Actually, I like that latter change). Redid it.
2. Myling (from Tome of Beasts) very flavorful, but very wonky to my tastes and mechanics that don't jibe with my preference.. Redid it.
3. Young Green Dragon - the most boring dragon of all! This one is up next and it needs some more interesting abilities.

My general philosophy with tweaking monsters, is that single monsters should have multiple flavorful/thematic powers and monsters meant to be faced in number should be more straightforward to remain easy to run, but maybe have a collective ability.

Since you mentioned will o' wisp, one of my favorite monsters although not for spamming. It is always a special encounter. This monster had the unique quality of having an exceptional AC without being something as impressive as a dragon or a tanar'ri (demon) and was immune to almost all magic. 5e version is a joke, has nothing to tell or to offer to the game, so I returned the old version and it worked wonders. It is so incredibly tough to beat that either the group has to understand that they have to flee or they have to use full synergy and strategy to beat it (depends on level if the second option is viable although I would never throw an 'old' will o' wisp to a party of 3rd level characters, obviously). For 4th level groups they have to retreat, for 5 level parties it depends.