Terrain assessment would be trees… lots of trees, the canopy is pretty full and allows some light in but blocks enough that the underbrush is somewhat sparse and consists mostly of patches of grass and thorn bushes. The canopy would probably range from about forty to forty-five feet above ground.
The trees are spaced probably around fifty to sixty feet apart and they are arranged in such a way that it would be apparent that ranged attacks would have to occur from fairly close, likely well within a hundred feet or so if not closer in order to get a good line of sight on a target so the characters can be fairly certain that the encounter is not taking place at great distances due to the terrain.
The ground is flat but not entirely even and there are some fallen logs as well as exposed roots that may provide some cover (Though this cover is more limited when the attacks are coming from above). The horses can be reached using a move action, and would require another action to mount up.
Hope that answers your question, if not let me know what else you would like to know.
So I guess I didn't do something right and my perception rolls that I tried to add in an edit didn't happen so I'll add them here. (Also I accidentally made my damage +4 when it's only +2).
Adsila and the Iliosani are getting very frustrating. They just won't go away. I don't know how we win this with the advantage they have with cover, ranged weapons etc. I'm sure poison darts will soon be raining down and a bad roll or two will doom us. Maybe we should race for our horses? Once we are on horseback they can't keep up with us even with the giant spiders. (Hopefully *smile*).
Quick note. In the initiative order you list Mradoric twice (And hey, if he can go twice I am NOT complaining!), and I do not see Lorilys or the orc listed. And from your note I assume that until the elves attack, and maybe blow a stealth roll, attacks against Adsila have disadvantage, right?
Ok, so since Carrick is going before the elves (Also his initiative is 21 as I rolled the advantage on this thread, I don't know how much it'll really matter, but just thought I'd point it out), he gets advantage on the first attack against an enemy that has yet to act in this combat. Has Adsila acted? This would negate the disadvantage and be a regular attack then for Carrick.
Aeric, would Faery Fire help in this encounter? If I wait until an elf is visible and cast It would it negate disadvantage on the elves that fail their save or would they still be considered hidden? I'm just considering options. The problem also is they are very likely to make their Dexterity saves anyways.
FF grants advantage if the attacker can see the target. It also negates invisibility, which these guys presumably aren't using. So no, it won't help while they're hidden. Aeric might impose a penalty to the affected elves' stealth rolls, but that'd be up to him.
On the other hand it would give us advantage to hit in the few moments they are seen. I think most of your buddies intend to ready actions to fire away when they reveal themselves to shoot.
The other issue is I don't know if you can hit more than one target. If they were bunched up, I'd say go for it, as someone's bound to fail the save and become easier pickings. But as it is…