Cthulhu MUD

Cthulhu MUD is one of many MUD (Read:Multi User Dungeon, essentially a text-based MMORPG) games, this one with a (surprise!) Cthulhu Mythos theme. While a bit more slash-happy than most investigator-style Lovecraft RPGs (say Call of Cthulhu (tabletop game) ) it nevertheless stays true to Lovecraft's original works. Like most MUDs, iy is easy to join and free-to-play, but with a learning curve. An Urban Fantasy with all the Swords and Sorcery (and EldritchAbominations and Black Magic), but in a distinctly Lovecraftian setting.

Tropes used in Cthulhu MUD include:

Alien Among Us - Alien player-characters will spend a lot of time in Human areas, and everybody except a number of law-enforcement officials will treat you as another human.
Ancient Astronauts - You can play as one.
Becoming the Mask - The Mask Self spell (necessary for an Alien avoiding attention from the local police) will literally turn you into the target creature as far as the game in concerned, even limiting what equipment you can use and changing you name in chat.
Cults - You can fight them or join them. Typically a Religion of Evil in the Cosmic Horror Story sense.
Dream Land - The original Dreamlands of Lovecraft. And you actually get there by dreaming.
Five Races - Instead of High Men or Elves you have Yithians, furry blue Zoogs instead of cute Gnomes, the (of course) mundane humans, the stout warrior Deep Ones, and Mi-Go as (abiet evil, technologically-advanced) fairies. All playable races, of course.
Jack of All Trades - Humans can pick from nine starter professions, while the other races are limited to one or two. Of course, all races can change professions later.
Magitek - Traditional magical spells and sorcery side-by-side with energy weapons and tripolymer armor, though the presence of magic may be justified by Elder Gods being invoked and, psychic powers and the scientific artifacts of lost races. Oddly, the magic is often even "more" effective.
Public Domain - with entire areas based on HPL stories (and those of Mythos writers in the same period) which would not get away with it otherwise.
Sanity Slippage - Looking at the wrong creature - or even being in the same room as it - will often knock a few points of the sanity score.
Squishy Wizard - Yithians, who spend a lot of time in others' bodies anyways. Keep in mind they are slug-cones with tubes and tentacles rather than regular High-men wizards, but they fill the same role.
Wizarding School - Miskatonic University, as well the Temple in Ulthar.
You Can't Get Ye Flask - Alas, you cannot go that way.