Have you ever crack open a book, be Bestiary or not, and witness a template that can become deadly when applied to the right creature?Or even better: have you seen a template that looks "harmless enough" at first, but became deadly as you found a base creature that could easily break the rules?
I'm so sorry, but... I keep finding that the Undead Lord template from Tome of Horrors can cook up some of the most ridiculous combinations ever made.
Basically, an Undead Lord makes any undead creature more powerful... with the ability to create spawns. At first, you tell yourself that applying it to a skeleton, a zombie, a ghost, a ghoul or a wight isn't too bad...
Try applying it to a Bone Ship (Bestiary 5)... or just about any giant-sized undead there is.
A Bone Ship is basially a sailing ship made of undead remains, totally eligible for the Undead Lord template. Here's the joke: Create Spawn will create MORE Bone Ships from any creature slain by the Undead Lord Bone Ship.
A sailing ship can contain 20 sailors and up to 200 passengers; a warship can contain 60 sailors with 160 soldiers... possibly more if 80 rowers are added in.
Congratulations! A single Undead Lord Bone Ship can kill off up to 220 or 300 creatures... and have its own fleet at its command in matter of minutes... because the create spawn ability doesn't state that the victim has to be of the same size, type or whatnot to become the same undead type of the Undead Lord.
Ok, while it's debatable whether or not the Undead Lord has to kill the creature itself, because a Bone Ship can aim at the hull, hit a powder keg and make the ship explode... but are creatures on board killed by the explosion or the Bone Ship that caused the explosion?
Still, so far, it's probably the template can be make things ugly in a matter of minutes.