colinfit20 said:
It doesn't matter if there's nothing in a room for them to hide, the point you're forgetting is that if the BBEG doesn't KNOW he/she is there they can still make a Hide roll, remember not every creature has darkvision/tremor sense/whatever!
The point about Hide is that they can't move or they break "cover", when they move they need to make a Move Silently check and they're stuffed if that is nowhere near as good as their Hide skill.
Actually, as per the PHB, you can't hide unless you have concealment or cover. So, if the room is bright enough to have nowhere that is considered concealment and no objects to give cover, no hide checks. As soon as you step into the room, everyone in the room can see you. Probably while coming down the hallway towards the room.
Even if the BBEG doesn't KNOW someone is there, he still has eyes and can look around. Some DMs might allow the PC to make hide checks in order to "sneak up on someone while their back is turned". But by the RAW, you can't do it.
colinfit20 said:
Anyway my point is that my character asked if being so small if she could fire a magic missile underneath the half dozen or so characters blocking the path ebtween me and the four skeletons that had been animated by the trap.
I was told no, which was harsh since being the only small szied character in the party should have made that easy, however even if your BBEG knew the room was empty unless they saw the character enter said room, they would have no reason to make a spot check upon entering unless the character breaks cover once they've entered.
Then your DM uses some strange rules. As per the RAW, you can target someone through any number of creatures. If you can see ANY portion of the enemy, you can target them, even if it's only their shoes or one of their fingers. Thus, anything less than full cover doesn't stop you from targetting them. Also, you can't use creatures as cover to hide behind. Plus, Magic Missile always hits, no matter how many barriers are between you and the enemy.
Second, Spot isn't an active action. You get a spot check automatically as soon as their is something to see without any action on your part at all. This is because most creatures don't stare in one direction without ever moving their head. Even while just standing there talking to someone, you occasionally look around as you scratch an itch on your back or stretch or do any number of things. Therefore, creatures are assumed to see in 360 degrees, as it is possible that they COULD be looking in any direction at any one moment.
So, in this case, you enter the room, everyone in the room gets spot checks against you, and you can't hide since you have no cover or concealment. Which means everyone in the room makes it automatically.
If you were to come with a house rule for sneaking up on someone who isn't really watching for you and might be distracted enough not to look up and see you, I might suggest making the enemy make a spot roll of DC 5 or 10 to see you approach with your skill not helping all that much.