"Three derro, as I told you. I would expect more of them at the main pillar, even though I did not see any. Weapons? Well, I would expect that the savant will cast spells, they usually do. The others had crossbows and swords." The scout looks about before she continues. "The bridge is 20 feet wide and we have to cross about 150 feet till we reach the platform. The other side of the wall ... and the passage we need to reach some 300 feet. There's a railing on both sides of the bridge and it provides some cover ... from the platform. The derro on the bridge though, well, they will see anyone passing by. I for one can neither fly, nor turn invisible. Yet if desired, I can move about unseen. We could sneak up unto the three derro up to, say 30 feet."
(The derro are on the middle of the bridge, so about 75 feet from either side.)