Regarding direct damage, the Phoenix from the Efreet or Dragon, or the Efreet from the Dragon or Phoenix, will only receive HALF the damage, since they attack with fire and only take half damage from fire attacks. I remember this clearly)
I don't want to say it's that important, but still there should be clarity, no need to look anything up, it's not critical, and there's barely enough beer for me anyway :D
PS I thought they were completely immune to fire. :( , and they take damage from direct attacks.