Elven troops disappear in Great Forest
 

While roaming around the map in the Great Forest, I lose Dryads, Sprites, Ents and Elves. The numbers reduce automatically. Is this a known bug? Is it part of the game?

That's not a bug. There are small bluish-black "clouds" in various locations. If you move over one, it kills a certain number of troops. There is a hut that gives you a quest to collect these "clouds" - you'll be given something that eats them and asked to fill it up and return it. So long as you have it, you can move over the "clouds" safely.

edit: Found the correct names. The clouds are Evlins and the thing given to you to collect them is Egnum. I believe there are a total of 15 evlins available to feed Egnum, minus the ones you've already encounted.

Thanks. I really think the game should have done something to tell me what was going on. Especially since it was so easy to get to the clouds before getting to the quest.

I agree - some kind of pop up announcing that troops were consumed by the evlin would help considerably. At least players would then know to avoid them.

I didn't know that,
 

I just always did that quest because it was fun. I lose enough troops on my own without having them disappear.