Incinerak, Worshippers of Fire.
Choosing this religion will allow you to summon Magma Demons, the Flame Warriors of Hell to your side.

At first glance, Demons appear to be a stacked form, Decent offense/defense, with the added bonus of the upgrading feature. (Any troops fighting alongside it are upgraded to the next level)
They bulk-up quickly at 3xp/health, and are cheap (75F to conjure, 2 Fury/fuel) They are the smallest of the Forms in Stature, and thus draw the fewest attacks their way.
However, they are the weakest form in terms of HP, and have the lowest Defensive ability at 88.

These guys are great early in the game or if your under seige on several fronts, their greatest asset is the morale boost they give to troops fighting with them, so try to keep troops with them.
Demons on their own, however, are quickly destroyed by concentrated groups of lessers once the game progresses & players have stronger troops, and are easy targets for some of the stronger forms.
If they have had several early fights & gained substantial extra health, they can be very useful further into the game.

Stacked with other forms & especially where troops are involved, thay can be very useful right throughout the game. If you find yourself wondering what all these stats & figures mean, please see:
wyrmmlore.com/evernight/newlounge/stats.html