The Overlord's Crown is an accessory given to all Darklings and boosts the stats of those who wear it (for both Darklings and adventurers) by an insane amount. It boosts AT by 300, DF by 250, MG by 200, and SP by 150. The only stat it doesn't increase is the HP stat which remains the same. Upon landing on another adventurer's town with this accessory, a monster will be summoned on that town. A normal player can acquire it by beating a Darkling in a fight and by choosing to steal the item afterward. The crown is worth 1000000G if sold.
In Dokapon Kingdom speedruns, the player(s) normally try to force another player to become a Darkling so that the Overlord Crown can be stolen from that player. With the crown, one could push past most of the rest of the game due to the sheer power of the crown giving one shot capability to the player allowing one to complete boss fights and story missions extremely fast. With the crown, almost every opponent is easier and takes less time to fight. Opponents such as the clonus, Rico Jr. and the Skeleton from the story quest might be just as difficult, as their stats are somewhat a reflection of the user's stats.