You're mistaken ;) An elemental is an elemental.

Isn't a phoenix an elemental? I don't think I have one on my computer, but there are a lot of different mods, although it's not listed as an elemental in the manual either.

What do you mean by "substantial"? 100 dragons? Well, yes, then it's a problem. However, this situation is only possible in single-player scenarios, and even then, there's always a way to avoid letting it drag on.

Why immediately 100 dragons? 15-20 and the rest are smaller units (especially if they are dwarves).

And you'll see a bunch of zombies slowly and not very effectively beating a bunch of skeletons, or vice versa... Meanwhile, the phoenix, along with the remaining enemy troops, will perfectly decide the outcome of the battle ;)

Isn't Darkness only used by the Undead? My army can also have trained paladins who attack quickly and effectively ;) And besides, is Darkness only strong because of its control/berserk abilities? You can cast Blindness/Slow on the phoenix. And in general, a summoned phoenix isn't that strong and is unlikely to compare to, say, 10 dragons. PS: Let's switch to "you," there's no need for formalities between students