In Neil Gaiman’s Norse Mythology, the giant who builds the gods’ wall is called the Master Builder.
The story retold by Gaiman comes from the Prose Edda account of the fortification of Asgard. A mysterious builder offers to construct an impregnable wall in exchange for the sun, the moon and the goddess Freyja. The gods accept only if the work is completed within one winter.
The builder’s stallion, Svaðilfari, works so efficiently that the gods fear they will lose the bargain. Loki transforms himself into a mare to distract the horse, preventing the builder from finishing on time. The enraged builder is then revealed to be a giant and is killed by Thor.
The Master Builder is a descriptive title rather than the giant’s personal name. That distinction separates this figure from named giants such as Thrym and Hrungnir.