Knights of Tezoth

Sounds more like you're buying a one-time effect that lasts until the first attack.

That's crap if so... So some weakling can strip the defense, and against Ardus coming right after, the city is left defenseless... Then let there be a choice: use the cancel or defend.

But if it's otherwise, you get unbalanced nonsense where Florenzan will pour a couple of actions into finances and calmly repel up to five attacks per turn, without any harm to the budget.