Battle of Keeper ' s Dale The Battle of Keeper ' s Dale , known as Yvonnel ' s Folly by the drow , was a short war fought by Clan Battlehammer and their allies against the drow of Menzoberranzan and their slave army of humanoids . Location . The environs of Mithral Hall . History . Causes . Matron Mother Yvonnel Baenre had wished to conquer the surface world in the name of Lolth for most of her considerable lifespan . Flush with power from her successful eradication of House Oblodra , Matron Baenre pressed ahead with a previously delayed plan to assault Mithral Hall , home of the dwarves of Clan Battlehammer . Possessing the trapped Gandalug Battlehammer , Matron Baenre had gained the knowledge of the city ' s defenses and was confident that victory would be hers . Recently returned from an excursion to Menzoberranzan , Drizzt Do ' Urden came back armed with the knowledge that the drow were coming to Mithral Hall , and so King Bruenor Battlehammer appealed to his allies for aid . Longsaddle , Settlestone and Silverymoon responded , pledging significant numbers of men for the coming war . Nesmé sent men as well , but only a small number - their relations still strained with the dwarves . Once the drow had marched from Menzoberranzan , clearly on their way to Mithral Hall , Belwar Dissengulp , a friend of Drizzt ' s , was given leave to command a force of deep gnome s from Blingdenstone . Limited by Blingenstone ' s King Schnicktick to 300 warriors , they left with haste to help defend Mithral Hall . Battle . The dwarven Gutbuster Brigade , Companions of the Hall and thousands of dwarven warriors fought valiantly and effectively in the tunnels beneath Mithral Hall , collapsing possible entrances to the Undercity whenever it looked like they would be overwhelmed . Despite the efficacy of their defense , the drow had the advantage , forewarned of most of the tricks and tactics arrayed against them , they broke through into the Undercity quickly , though with higher than anticipated casualties , including Uthegentel Del ' Armgo at the ' hands ' of Bidderdoo Harpell . At that point , on the advice of Methil El - Viddenvelp , Jarlaxle commanded his Bregan D ' aerthe mercenaries to begin avoiding the fighting while the drow marched their reserve forces toward the Undercity . While a division of dwarves held the eastern side of Keeper ' s Dale itself , the humans , under the nominal command of Berkthgar , fought off a second wave of foes on the western side . Armed with magical pellets that would counter drow " darkness " abilities and blind their foes , the humans appeared to have the upper hand , especially since the drow did not fight with any real semblence of unit cohesion - selfish by nature as drow were . However , despite these apparent advantages , the humans were horrendously outnumbered and quickly outmaneuvered . Drow wizards blasted apart men and only a drow tactical misstep combined with the magical might of Alustriel Silverhand saved the human force from being massacred . Shortly afterward , the deep gnomes emerged from the Underdark onto the surface not far west of the fighting and opened a second front behind the drow lines . Besnell , the elven commander of the Knights in Silver detachment was felled by goblins shortly before the remaining human forces , depleted to roughly two thirds of their original number , could regroup . Dawn was the real turning point in this battle . As the rising sun blinded the drow army , Berg ' inyon Baenre , who led the surface assault , was filled with doubt and quickly issued a retreat order . The Companions of the Hall had decided early on that the only way to ensure victory would be to eliminate the drow commander , whomever that might be . Drizzt was dismayed when he saw Yvonnel was leading her forces herself when they came upon the drow command post hidden in tunnels behind the enemy line . With no choice but to attack the command post , they did so with vigor and determination . Unknown to all assembled , a glabrezu beholden to the balor Errtu had brought a sapphire with it when summoned that radiated an Antimagic field . On orders , it released the sapphire from a protective case when the Companions attacked . With the drow so highly dependent on magic , the Companions took the initiative to bring their superior skill - at - arms to bear during the instant that the drow were denied their protections , eliminating all of the assembled drow priestesses before they could recover from the shock . Aftermath . Matron Zeerith Q ' Xorlarrin ordered a retreat from Mithral Hall ' s Undercity , more concerned with her own status than continuing the fight . Berg ' inyon ' s forces regrouped with Bregan D ' aerthe on the way back from the surface . Triel Baenre , as Yvonnel ' s heir cemented her much more shaky rulership over Menzoberranzan , later going on to conquer Blingdenstone as a show of power and act of revenge for the help they gave the dwarves . Many of the city ' s refugees went to live in Mithral Hall , where they were welcomed . Although tinged with great sadness over their losses , the victory of the surfacers was hearty . Berkthgar began talking about and eventually took his remaining followers back with him to Icewind Dale whereupon Settlestone was repopulated by dwarves . Terrien Doucard took over from Besnell . Drizzt and Catti - brie left the Hall to go adventuring and King Bruenor abdicated his throne to Gandalug , taking Regis and a few loyal dwarves with him back to Kelvin ' s Cairn . Combatants . Casualties . Notable casualties included the deep gnome Firble , Regweld Harpell , the Silver Knight Besnell , Auro ' pol Dyrr , Uthegentel Del ' Armgo as well as Quenthel , Bladen ' Kerst and Yvonnel Baenre .