v.129 - Mark of Honor: Kanna Update Notes

I'm not sure how it works technically, but you can definitely see the difference once the skill is cast, especially on a high spawn map like Roids.
And it works for the entire map, so yeah it would definitely be useful as a "Spawn Mule"

From my direct experience, it doesn't reduce the spawn time but it does increase the spawn numbers. The test was at the Toy Room. The toy room is 4 Twisted Jesters on the standard spawn tick of every 10 seconds. With the two demons playing catch having been summoned, the spawn changed to 6 Jesters every 10 seconds.

I really hope this works at Castle Golems.