In order to read this text, a separate item (an oddly cut lens of bluish glass) is needed. Both the codex and the strange glass needed to read it were found among the effects of a promising Austrian physicist following his disappearance in 1918, and they currently reside in the home of an heir. The original Greek text appears to be the product of an unknown and esoteric school of Pythagorean thought. Its theme is the relationship between time and geometry.

The Codex ends with a strange diagram. When the colored glass reaches a particular symbol at the center of the diagram, the reader will see something like a wolf's eye glaring back at him from the glass, seemingly peering hungrily into his very soul (this experience costs 1/1D3 Sanity points). Only when the glass rests upon this symbol may the Codex's lone spell be cast:

Contact Lord of Tindalos: This powerful spell costs 24 mp to cast, and 1D3 Sanity points. When cast from the Tindalosian Codex (with the colored glass in its proper place), it succeeds automatically, with the furious lord emerging from the glass. The lord brought forth by this spell has the power to transform the contactee into a Tindalosian hybrid, but it will expect an exceedingly dear payment in return. If not satisfied with what the contactee has to offer, it will carry him back to Tindalos to be hunted and feasted upon across multiple timelines. Statistics for the lord of Tindalos and the Tindalosian Hybrid are found in the Malleus Monstrorum.

Greek language, -1/1D3 sanity; +3 Mythos; Spells: Contact Lord of Tindalos; 2D4 weeks (average 5 weeks) to study and comprehend