Alter-time was a broad term used for any temporal mechanism, environment, or structure of causality that went against the Protocols of the Great Houses or the history the Great Houses dictated.

Grandfather Paradox became a pariah in the eyes of the Homeworld due to his alter-time experiments. It was speculated that when Faction Paradox performed the loa rites, they were merely accessing alter-time mechanisms embedded in history by the Grandfather. The Eleven-Day Empire was considered the first alter-time environment set apart from history. Many traits and abilities displayed by the members of Faction Paradox were dubbed as alter-time. (PROSE: The Book of the War)

Memecores were used to create alter-time environments. Goralschai used a memecore to establish the Netherweald in the Nemontemi. (PROSE: Against Nature)

Before the War in Heaven, Avus travelled to another alter-time realm. This realm contained a remnant of the pre-universe, and Cernunnos used the space to plot the War. (PROSE: Cobweb and Ivory)

The Mal'akh domain was another alter-time environment that often interacted with Earth, (PROSE: The Book of the War) called the Kingdom of Beasts. (PROSE: The Adventuress of Henrietta Street)

Anti-time, anti-matter and Schrödinger's Virus were all alter-time states. The Osirians inoculated Apep with many alter-time states, including these three, in order to make him "unanchored", freeing him from the control of the Great Houses altogether. This ruined Apep's original purpose as a weapon the Houses could wield against the Osirians' sentient sun Ra, although it also drove Apep insane. (PROSE: Going Once, Going Twice)