Castle Quest 2

Castle Quest 2 is a text-based browser game that's been around since 2003. For years it managed to get by without advertising or donations with its hosting fully paid for by its creator. Nowadays it's suffering a bit from a shrinking playerbase and it has a small, barely noticeable ad now. The game is divided in ages, each one lasting about a year. At the end of an age there is usually a big storyline event followed by a full reset.

Each player is a mage in a castle that trains and equips a small army of creatures. The mages themselves never battle directly, all the fighting is done with the creatures. There are four classes with about ten races each. A mage does not have to stick to his own class but the skillpoint investment to use the best creatures of a different class is fairly severe and mages that can use the best creatures of two classes are very rare.

Tropes used in Castle Quest 2 include:

Class and Level System: A player choses one of the four classes. Every few levels a new building is unlocked and can be built if all previous buildings of that type are built and the player has enough granite. Summoning the best creatures requires a specific and heavvy investment of skillpoints and the buildings get quite expensive after a while. Usually only dedicated shopmages will build all the buildings and sell the creatures they can summon to other players. Most players only build the buildings that increase their maximum army size.
Crippling Overspecialization: There simply arent enough skillpoints to do everything. Teamwork and planning ahead is essential. Players usually divide themselves unofficially into 'cursers', 'travelers', 'raiders' and 'shops'.
Critical Hit: Rare. Only pit worms and imlers can crit. Pit worms have items that give them a certain % chance to do double damage. Imlers have a certain % chance to do the opponents damage in addition to their own.
Hit Points: All creatures have health.