Bertelm is a member of the original Alliance forces that came through the Dark Portal with legendary heroes General Turalyon, Archmage Khadgar and Ranger Alleria Windrunner. As a part of the Sons of Lothar he worked specifically with Force Commander Danath Trollbane in tracking down Ner'zhul. Unfortunately we know how that story played out. (If you don't it is all contained in the book Beyond the Dark Portal by Aaron Rosenberg and Christie Golden.) Now he calls the Allerian Stronghold in Terokkar Forest of Outland home.
As a result of his isolation Bertelm has no difficulty working with the High Elves, nor confusing them with the Blood Elves because these are all recent changes for him. In fact it seems that Bertelm has developed a bit of a crush on one of the new arrivals to the stronghold, the seamstress Ros'eleth. In his desire to get to know her better he laments the loss of all the taverns back in Stormwind and plans for how he can convince her to go for a "nice walk in the woods" with him.
As a quest giver Bertelm has you assist him with both his job AND his personal obsession. When you first meet him, Bertelm shares his belief that Ros'eleth must have feelings for him as she winks whenever he goes to pick up something from her. So he wants to create a special garment using local materials to impress her. Unfortunately work keeps getting in the way, limiting his ability to gather all the materials. Bertelm asks for your assistance both in thinning out the ranks of the Fel Orcs in the area as well as gathering up some worg tails and a specific worg's hide for his "masterpiece" garment. Bertelm also sends you to one of his operatives, a High Elf rogue by the name of Theloria Shadecloak to see what all she has discovered.
Theloria will tell you that much to her dismay the Blood Elves are working with the Fel Orcs. When you slip inside the Bonechewer encampment to remove the Firewing Liaison you will see a paper on the ground. Pick that up and take it back to Bertelm for analysis. Bertelm will then inform you that despite all ideas to the contrary the Blood Elves are not just working WITH the Fel Orcs, they are actually the ones in charge, using the Fel Orcs as a diversion for the Allerian forces. Why he doesn't know but it means his seduction of the lovely Ros'eleth is going to have to wait.
One last item of note about Bertelm, he is slightly taller than the average human male. This may have to do with the in game mechanics that make bosses larger than average (Think of the changes in Tirion.) Not all npcs are effected this way but oddly enough Bertelm is one of them.