Some point during this run, I found this particular area in The Vault that kept spawning clusters of the same enemy every time I go away and come back to it. I never found out why this bug was happening and how to replicate it.
One or more Kranuhiisi will also spawn whenever a Toimari is damaged.
I know that if there isn't space to spawn at least gold, the way the game engine handles it to spawn it at the first available spot moving vertically upwards.
Assuming that the monster spawn functions the same way -- which seems like a reasonable assumption -- maybe something like a Toimari stained with Ambrosia and also somewhere they can be damaged in a tight area below the area in question would do it?
I don’t think it was a situation where there was a Toimari below that spot getting damaged because there was an opening below on screen where all the Kranuhiisis kept spawning. Although, I think it probably has something to do with that mechanic being bugged after I killed a Toimari.