Poisonous is a special ability of Wyvern Monarchs. It may occur after they have attacked or retaliated target creature stack. The chance of poisoning the target is 20%. Poison and its effects can only be removed with the Cure spell.
When poisoned, the target stack's maximum health is decreased by 10% for every combat round for three rounds. The reduction is always calculated from the creature stack's statistical maximum health. The effect is cumulative, which means that after three rounds the poisoned creature has lost 30% of its maximum health. After three rounds, the creature is no longer poisoned, but the maximum health remains decreased. The same troop can be poisoned again, but the maximum health will decrease only up to 50%. The reduction of maximum health does not kill the creatures, but it makes them more vulnerable.
The possible poisoning effect takes place after the attack and before the stack has chance to retaliate. The effect of poison has multiplicative effect with Ghost Dragon's aging ability. This means, that the creature stack's health could potentially be quartered.
Creatures with poisonous special ability:
While Wyvern Monarch's special ability may seem useful and even powerful, the problem with it is that quite often combats are resolved in the first few rounds. While the chance to poisoning the enemy is only 20%, it is more than possible that the poison ability will not emerge during the battle, or at least not in time to make a difference. Additionally, Monarchs are typically the first creatures in Fortress armies to reach the enemy, which usually also means they are the first ones to get hit. This combined to the fact that Monarchs' health is quite low compared to its level, makes Monarchs number typically small at the end of the game. At best, Monarchs will poison one or two stacks (with retaliation) at the first round of combat, and the poison will have time to affect the whole three rounds reducing the maximum health of the stacks by 30%.