It is not enough to calm the raging horse to become a king; one must ride (or in some versions, be ridden by) the great beast, and then must slay Glastrier to calm the raging winter once and for all. Of course, no proper king lacks a mount, and death is not the end of its journey; this ancient ritual may kill Glastrier, but its spirit remains bound to the king in the form of a Spectrier, unburdened by ice.
Spectrier can not spend every moment as the king's steed, for Calyrex has many duties to attend to, and can not always restrain its malice. When left alone, Spectrier gallops across the Crown Tundra (for no pen can contain it), absorbing the souls of the damned – which is to say, any souls unlucky enough to cross its path. Calyrex sought to control Spectrier's appetite by offering it the role of executioner, but the people feared its wrath too much to risk attempting capital crimes; perhaps the memory of this, with a side of just world hypothesis, is why this pokemon is so commonly described as targeting the souls of "the wicked". Only the breeding of many carrot species to create the Shaderoot, a flavor perfectly suited to its palate, could finally calm Spectrier down and satiate its hunger in the king's absence.
Curiously, in one variant of the tale, Glastrier and Spectrier were not the same horse at all, but twin steeds who pulled Calyrex's chariot across the land as it conquered the Crown Tundra. If this tale is true, then Calyrex must be regarded not as a king of plenty, but a horrific tyrant, for no land ought to be cursed simultaneously by the apocalypse of two such equines.