Triangle Wizard is a real-time roguelikelike. It combines an ASCII character art-style with vector graphics and nice magical effects. The gameplay reminds one of Diablo, especially the first one, but is a lot less forgiving, and contains many more random elements. Two major things it retains from Diablo 1 are the shrines which, like in Diablo, can permanently change your character (sometimes in a bad way), and the random item generation based on prefixes and suffixes along with socketed items and unique items. Also like in Diablo 1 the quests (apart from the main quest) only have a certain probability to show up meaning not every quest will be available every game. In addition there are also some short randomly generated quests available which are usually risky, but have good rewards.
It contains a large variety of monsters, bosses, and unique creatures. And also many races and classes to play. Most levels are randomly generated, including some quest levels. Non-random levels are reserved for the boss encounters. There are also some random special levels which may appear in some games, like the Tournament (where dungeon denizens fight for the favor of their boss) or the Hall of Mirrors (where all projectiles bounce on walls). When leveling up (and via different methods) talents can be obtained which can change your character or spells in unique ways, for example allowing you to use your Fireball spell as a mine, or accompanying the Teleport spell with a Shockwave spell.
There is a particular focus on interaction with the environment. Walls can be destroyed (sometimes revealing hidden rooms), water and lava can affect and be affected by magic, and knocking creatures into spikes hurts them. Water can be tainted (which will spread over time) and there are many more such interactions. There are also interactions between spells allowing one for example to counter or reflect spells.
The game also features a fully-fledged deity system with a large number of deities to worship or offend. Each of them offering unique boons or banes (if you anger them). Disciples to deities can be found in the dungeon and some items might be dedicated to certain gods. Allies can also be found to join the player, and can be given items to use. They can also be given complicated commands using a tactics screen (while the game is paused).
The main story involves the player attempting to invade Castle Everdoom and slay its evil master, the Nameless One. However this story can be changed depending on player choices (you can for example worship the Nameless One), and multiple different endings are possible.
There is an in-game wikipedia-esque help system called the Trianglopedia which (with a toggle) can also display spoilers.