I feel like it's kinda pointless to have Cerberus as a Myth spell when Myth already has Orthrus. Any changes you make are irrelevant. And there's also the fact that all three of the Cereberus' heads have t do something, preferably attack, but the whole triple-attack ability is a Balance ability. This is why I used Cerberus as a Balance spell.
The new myth spell should be gryphon that attacks all eniemeis 995-1255 plus stun on all eneimeis get rid of all wards and blades not traps! The would look like an angry gryphon in a nest then swoops down and attacks
