The most difficult alternative

Nature also faces a very difficult choice on the fourth level. Both options are good. The combination of water elementals, griffins, and winged demons is very effective and allows you to crush even three times superior forces without losses, but if the enemy army has units with immunity, this tactic fails immediately. Griffins, phoenixes, and praying mantises is a universal combination, but it inevitably leads to losses in battle, even against an enemy army of equal strength.

By the way, I've never checked, but I think that a Barbarian with a Grand Master combat skill, around level 20, would hardly be able to defeat five phoenixes. :) They would devour him without any difficulty. Although, maybe I'm wrong? :)