"And the unicorn evils run them through;
Split all ends up they shan't crack" (16-17)
The 'they' in stanza two of "And Death Shall Have No Dominion" refers to the dead. Thomas uses the second stanza of his poem to focus on the strength of the spirit and faith's role in death; he mentions very forms of torture "twisting on racks" and being "strapped to a wheel," but even these forms of death cannot quench the force of the spirit and its role in the natural order.
Dylan's metaphorical diction of "unicorn evils" suggests something unnatural and unwholesome; typically unicorns are mythical beasts with a positive connotation, but here Thomas' choice of the word connotes something that does not belong to the natural order of things. He uses what is typically a noun, "unicorn" as an adjective to describe evils; the juxtaposition of his word choices suggests an ancient, savage evil, but even in the face of this being possibly gored by this evil, the speaker argues that the dead's spirit will overcome and endure. He reinforces his imagery of being "run through" on the following line, using the word "splitting" to reference a physical tearing of the body and soul; even so, Thomas maintains that the human spirit will not rupture or "crack" against brute force. According the the speaker of the poem, man's spirit lives on, even through violent deaths or suffering, because it belongs to the natural order of the world.