Hiring monodrones is usually cheaper. They are the simplest Modrons, and they would be perfectly willing to work for a Lawful king (the evil-good axis doesn’t come into play) because it increases the amount of order in the multiverse. But every modron has Truesight.
Hell, maybe hire a whole team of modrons. Monodrones to stand watch at all ingresses, with orders of “raise an alarm if you see any disguised shapeshifter enter through that window / door / arrowslit / whatever”, and duodrones with orders of “patrol the castle and raise an alarm if you see any disguised shapeshifter”.
Hiring monodrones is usually cheaper. They are the simplest Modrons, and they would be perfectly willing to work for a Lawful king (the evil-good axis doesn’t come into play) because it increases the amount of order in the multiverse. But every modron has Truesight.
Hell, maybe hire a whole team of modrons. Monodrones to stand watch at all ingresses, with orders of “raise an alarm if you see any disguised shapeshifter enter through that window / door / arrowslit / whatever”, and duodrones with orders of “patrol the castle and raise an alarm if you see any disguised shapeshifter”.