During prep I made a list of all of the creatures in the 5e Monster Manual that could potentially be playable character races. You could consider this a shortlist for revamping Monster Mythology, but I'm using this as a list of potential NPC races:
Mind Flayer p.222
Umber Hulk p.292
I even made a rando generator for this list
The Sunday game, in contrast, is going to embark upon a traditional dungeoncrawl using the Dwimmermount megadungeon and, coincidentally, 5th edition Dungeons & Dragons. I've been reading the book and taking notes for the last few weeks so I think I'm familiar enough with the upper levels of the dungeon that I shouldn't have any problems - I'll share more about the extensive prepping I did in a future post.
For now, the most surprising thing for me is reading the spells in 5e D&D. The way cantrips work is so much simpler now, but also more powerful. You don't need to worry about light if you have a single magic-user in your party. The cleric has become a much more valuable utility class considering how powerful the create water and purify food spells have become. Just from reading the new rules I would be interested in running a 5e game where the PCs can only be fighters and rogues.
Did you know green slime has been nerfed from 'monster' to 'hazard' in 5th edition?
Here is my version of Green Slime as a monster in 5e D&D
Green slimes always move towards the closest creature they can detect.
Armor Class: 8
Hit Points: 22 (3d8+9)
Speed: 10 ft., climb 10 ft.
STR 15 (+2), DEX 6 (-2), CON 14 (+2), INT 1 (-5), WIS 6 (-2), CHA 1 (-5)
Damage Resistances: acid, cold, fire
Damage Immunities: lightning, slashing
Condition Immunities: blinded, charmed, deafened, exhaustion, frightened, prone
Senses: tremorsense 30 ft., passive perception 11
Challenge: 2 (450 xp)
Amorphous. The slime can move through a space as narrow as 1 inch wide without squeezing.
Spider Climb. The slime can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Slimed. When moving, green slime can enter other creatures' spaces. Whenever the slime enters a creature's space, the creature must make a DC 12 Dexterity saving throw.
On a successful save, the creature can choose to move back 5 feet or to the side of the slime. A creature that chooses not to be pushed back suffers the consequences of a failed saving throw.
On a failed save, the slime enter the creature's space and makes contact with the creature's body. The creature takes 10 (3d6) acid damage and is slimed (see below). Creatures that are slimed can move and act, but take 10 (3d6) acid damage at the start of each of the slime's turns until they are no longer slimed.
At the start of your turn, you must make a saving throw - follow the rules for making death saving throws, however taking damage or being reduced to 0 hit points will not cause you to fail a slimed saving throw. Failing three of these slimed saving throws turns your character into another green slime, which either adds it's mass (and 22 hit points) to any existing green slime in your space or acts as an independent and new green slime.
Succeeding at these slimed saving throws does not throw off the slime, it merely delays the inevitable.
While you are slimed, the green slime can be scraped off, but whatever implement used to scrape it off takes 10 (3d6) acid damage when it comes into contact with the slime (assume wood is a fragile material and metal is a resilient material, page 247 of the DMG).
Disease. Any magical effect that would cure a subject of disease, including lesser restoration or purify food and drink, when cast upon green slime will instantly destroy it.