This spell is a part of the Time Distortion spell chain and can be found in the Time Distortion rune stone.
Time is not fixed. This is perhaps the first and most important thing the posteramancer learns. The pace at which time moves is not a law but a condition, and conditions can be altered by those who know how. Most people experience time as a steady and impartial current, carrying everything forward at the same rate without preference or flexibility. The posteramancer experiences it as something considerably more negotiable. Compressed Time is that negotiation applied to the act of casting itself.
When this spell is cast the posteramancer reaches through Doom into the time that surrounds the target and simply pushes it together, compressing the moments that spell casting normally requires into a tighter, faster sequence without reducing the integrity of the cast itself. The magic does not become less precise or less powerful. It simply arrives sooner. All of the target's spell casting speeds are halved for the duration, rounded down, the time that spell casting normally occupies squeezed into a fraction of itself. A spell that would take 8 rounds to cast takes 4. A spell that would take 3 rounds takes 1. Even a spell that costs only 1 casting speed becomes a free action, castable once per round with no effect on the target's runic speed whatsoever. The posteramancer finds this deeply satisfying, unaware of the inching closer to Doom they have come for though they do not know it, they have aged a day with the casting of this spell. Time, it turns out, has considerably more give in it than most people ever bother to test.
Armor Effect: Compressed Time
Spells cost 1 less casting speed to cast.