D&D Dungeon Masters like Mercer and Woll on how to make memorable NPC introductions

While raiding Xanathar’s lair in the midst of playing through Waterdeep: Dragon Heist, the bard made a disastrous decision. He threw the last bead from the Necklace of Fireballs not at Xanathar, but at the large pile of gunpowder barrels behind the Beholder gang boss. The ensuing blast sent the group careening through an underground cavern, swept away in the currents of a glowing river. The bard himself died, along with the ranger’s panther companion. As they pulled the bard’s lifeless body onto a random shore, a figure emerged from the darkness, threw back her hood, traced an arcane sigil onto the ground, chanted a language they couldn’t understand, and bound the bard’s fading soul onto a nearby suit of armor. “I’m Khatska,” was all she said.