I don't have a better pic
I'll say what wikipedia say:
Arx Fatalis is a partially open source first-person role-playing video game for the Xbox and Microsoft Windows, released on November 2002 by Arkane Studios. Arx Fatalis (lat. "fatal fortress") is set on a world whose sun has failed, forcing the above-ground creatures to take refuge in subterranean caverns. The action in Arx takes place in one of these large caves, where inhabitants from all races such as Trolls, Goblins, Dwarves, Humans, etc. have made their homes on various levels of the cave. The player awakens inside a prison cell and, after making his escape, eventually discovers his mission is to subvert and imprison the God of Destruction, Akbaa, who is trying to manifest itself in Arx. There is no dialogue system in Arx Fatalis. Rather, the player is able to make choices through actions which lead to different consequences. There are also multiple ways to finish quests and the player can progress through the game in several different ways. For example, the player can use force to kill enemies and break down doors, or they can use stealth and avoid enemies. One of the intuitive interfaces in Arx Fatalis is the spellcasting system. Using the mouse and the Ctrl key, runes are drawn in mid-air with mouse gestures, which must be correctly drawn, in order to successfully cast a spell. The player can find or buy different runes as gameplay progresses, combinations of which unlock new spells.
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Website:
Arkane Studio
TL;DR? In two words: amazing game