John Gardner noted that the twelve chapters of Grendel correspond to the twelve signs of the zodiac, both in imagery and in the characters featured in each one.
Chapter One is Aries, the Ram. It begins with Grendel frightening off a ram that has come too near his territory. In this chapter, the cyclical view of the universe is expounded, as Grendel notes that he is trapped in the "progression of moon and stars."
Chapter Two features Taurus, the Bull. A bull attacks the tree-trapped Grendel on his adventure in the outside world.
Chapter Three corresponds to the Twins, Gemini. This chapter discusses double-talk, as the Shaper creates one reality to stand alongside the experienced reality.
Chapter Four belongs to Cancer, the Crab, known as a nourishing force in some astrological belief systems. The Shaper's songs have created and nourished a religion that gives the people a more fixed alternate reality to believe in against their own miserable, hard existence.
Chapter Five is the chapter of Leo, the Lion. Leo is known as a dramatist to some, and in this chapter, Grendel seeks to know his role in the greater scheme of things. The dragon offers him a part to play, but Grendel cannot accept that this is his destiny.
Chapter Six refers to Virgo, the Virgin, in Grendel's comment, "So much for the harvest-virgin." Unferth the would-be hero attempts to do honorable battle with Grendel, only to have his naive view of life trampled underfoot by Grendel's refusal to fight him.
Chapter Seven corresponds to Libra, the sign of balance and conciliation. Here Wealtheow reconciles Hrothgar and her brother Hymgod, as well as their respective warriors. Even Unferth finds some balance in Wealtheow's compassion toward his ill-charmed life.
Chapter Eight introduces Hrothulf, the potential usurper, as a "sweet scorpion," thus connecting to the astrological sign Scorpio.
Chapter Nine alludes to Sagittarius, the archer, in the scene of a Scylding hunting and killing a hart with a bow and arrow. Sagittarius is pictured as a centaur, half-human and half-horse, suggesting a need to reconcile two different natures. Here we see the priests attempting to promote a religion that they themselves do not believe, giving the people of the village hope while simultaneously recognizing that such hope is based on false knowledge.
Chapter Ten belongs to the pessimistic Capricorn, the Goat. Grendel has reached the nihilism of Nietzsche in his philosophical quest, seeing himself and all others as alone and abandoned in an impersonal universe.
Chapter Eleven is the chapter of Aquarius, the Water-Bearer. Aquarians are described as interested in understanding life's mysteries. Grendel has come through his philosophical journey, but he is no wiser other than in the knowledge that no system of thought will satisfy him.
Chapter Twelve refers to Pisces, the Fish. The number two, as well as an inherent dualism, is often connected to Pisces. In this chapter, Grendel fights Beowulf, his opposite number, and is defeated by the latter's empiricism. Thus, his universe of one has temporarily become a universe of two, and this duality ends by destroying him.