Melech died during the campaign book D&D 5e - Tomb of Annihilation

Level 6
Class Warlock
Race Tiefling
Align Neutral Evil
Diety Cthulu

STR 10
DEX 13
CON 13
INT 12
WIS 10
CHA 17

HP  46
AC  12

Melech when leaving the Heart of Ubtao did several things to make Valindra Shadowmantle remember him.  Besides looting her lair, Melech also destroyed her teleportation circle.  Unbeknownst to  Melech, Valindra swore revenge.  It took her 24 days to track down Melech.

Valindra waited until the party was engage with a group of Grungs.  While turning visible, she cast ray of frost at Melech, which missed him.  Determined to not make that mistake again, she followed up with fireball.  The fireball killed half of the Grungs and Orvex the translator.  Melech and Zay were knocked unconscious and dying.  Valindra walked over to Melech and whispered something corny about respecting the lich.  At that point, she pointed her fingered at Melech and he disintegrated into ash.

Killed by: Valindra Shadowmantle