This is similar to our earlier post about games like Diablo 3, but this time it is about Diablo 3 Free to Play alternatives. Please note that many (if not all) of these games have some sort of cash shops with micro transactions, so they aren't completely free, but these cash shops are completely optional and you can play as much as you like without every paying anything.
Mythos
This game 4 different classes which are Cyclops, Humans, Satyrs, and Gremlins along with 3 different classes.
This game reminds you of Diablo in almost everything it does, but that isn't necessarily a bad thing right? Anyway the game's official website can be found here, or if you want to skip straight to the client download click here.
Battle of the Immortals
This Diablo 3 Free to Play alternative sports some cool features not found in other games, such as weapons leveling up the more you use them. This game also features an in-build bot (no joke) but can only be used for a specific time period each day. The game features Berzerker, Champion, Heretic, Magus, and Slayer, and another TBA class being the Summoner.
The main site can be found here and the client can be downloaded here.
Mytheon
This Diablo 3 Free to Play alternatives is currently in the beta but they are accepting new players at the moment of this writing. This game's theme is a mix of Greek, Roman, and Egyptian mythology. This game features very well written English dialog (unlike some of the Chinese games), instances for areas outside of towns, as well as a unique spell system where 5 skills are randomly drawn from your collection and force you to use them. As soon as you use one, it is replaced by another one from your collection. The game's classes are Eidolon, Elementalist, and Warcaster.
You can sign up for the beta here.