YMMV / The War of the Ancients

• Big-Lipped Alligator Moment: Near the beginning of the first book, Rhonin and Krasus spend a night on an island where they're attacked by undead. These undead are notably different than any undead encountered before in the franchise, including having strange, dream-invading powers, and are revealed to Rhonin's shock to be distinct from, and even more unholy than, anything the Lich King perpetrated. This ends up having no bearing on the plot whatsoever, and even though Krasus vows to come back and deal with it after their quest, its never brought up again.
• Complete Monster: Azshara, the Light of Lights (who also has a brief cameo in WoW: Cataclysm), is the former ancient queen of the Night Elves who, in her endless goal to obtain power and perfection, nearly led all of Azeroth to total ruin. 10,000 years ago, Azshara used her magic to enthrall her people to love her without question while also seeking to purify the world of any she deemed imperfect, who included all but herself and her Highborne servants. While attempting to enact this purification with the power of the Well of Eternity, she caught the attention of Sargeras, creator of the Omnicidal Burning Legion. When he offered to aid in her goal in exchange for allowing his armies to rampage over Azeroth, Azshara agreed without question. Her actions to satisfy her own limitless vanity led to the War of the Ancients, the deaths of countless innocents, and the breaking of the entire world. Azshara then makes a deal with the Old Gods, who turn her and her servants into the first naga. As their Empress, Azshara can be held directly responsible for every atrocity committed by the naga in WarCraft 3 and WoW.
• Ensemble Dark Horse: Unlike all the other main characters Broxigar Saurfang has not really been important to lore before or since these 3 books but he beloved. Having an interesting and tragic backstory, a well-received character arc, and having one in the most badass moments of the entire series where he Hold the Line against hundreds of demons and even Sargeras.
• Moral Event Horizon: Most of the Highborn cross this with their deal with Sargeras, but Azshara doing so is especially heinous as she welcomes seeing the Burning Legion wiping out all life on the Azeroth, save her and select few feels are worthy to live.