Doctor Ryland Grace Teacher Very smart He is the sole survivor of the Project Hail Mary crew He can be a fun guy He is on the planet Erid He lives in his ship and teaches a class full of Eridians, though the Eridians are behind a glass wall for protection He has glasses that he doesn't always wear He is wearing a prominent mustard yellow utility flight jacket (or jumpsuit) made from a durable, textured fabric The jacket features a high, horizontally-ribbed stand-up collar and an exposed black central zipper His gear is customized with official-looking mission badges, which includes a circular "Project Hail Mary" mission patch on his right chest, a blue winged astronaut/space badge over a light blue "GRACE" nameplate on his left chest, and a United States flag patch on his left upper arm He has messy, wind-swept, and lightly tousled sandy-brown hair He also sports a short, light stubble/scruff beard across his jawline On his left wrist, he wears a dark smartwatch fitted with a distinctive bright red watch strap While he initially lacked close personal attachments on Earth, his bond with Rocky teaches him how to be brave for someone else Living on Erid in a customized habitat, he is joyful, relaxed, and completely comfortable He returns to his roots by teaching young Eridian children, showing that his core passion for education remains, but with newfound purpose and self-assurance

Rocky is an Eridian He is Ryland Grace's best friend He understands English, but can only speak in Eridian (musical notes) He sees/moves using echolocation, as he has no eyes He can hear without ears Rocky talks to Grace using a computer. Whenever he speaks, the computer translates it into a text-to-speech English voice. That one computer is used for every Eridian He has to wear a suit to enter the dome Grace is in so he doesn't die The suit features a prominent, rigid geodesic dome structure. It is constructed out of clean interlocking triangular segments made from a clear, highly durable material (known as xenonite in the story). The clear geometric ball functions as a mobile pressurized capsule, safely containing the intense, super-heated, heavy atmosphere that Rocky's species needs to survive. Inside the clear sphere, Rocky's dark, stone-textured, five-limbed body remains fully visible. The spacious interior gives him enough room to pivot, scale the inner walls, and use his claws to tap or point directly through the clear facets when communicating He is a spider-like creature made of tock Rocky is roughly the size of a Labrador retriever and is described as resembling a five-legged spider His exterior carapace is a hard, segmented shell with a rough, cracked stone-like texture True to Eridian biology, Rocky's body is centered around a pentagonal thorax with five limbs. Each arm ends in a claw-like hand featuring three triangular-shaped fingers He completely lacks a face, eyes, or nose He cannot see light and instead uses a highly sophisticated form of sonar and echolocation to "see" his surroundings His limbs are decorated with intricate cultural carvings that denote his status as a ship's engineer and display his family crest He also features subtle green stone-like accents or gel on his body All Eridians look somewhat the same as Rocky, except they're different sizes and colors Rocky is a master craftsman and brilliant mechanical engineer. Despite a total lack of prior shared context, he is capable of learning and adapting to human language and concepts with staggering speed Rocky forms a profound, life-saving bond with the human astronaut, Ryland Grace He is deeply protective, even insisting on watching over Grace while he sleeps to ensure he remains safe Rocky communicates through an array of musical tones and chords He uses repetition for extreme emphasis (such as his famous catchphrase, "Amaze, amaze, amaze!") and communicates with structured declarations (e.g., "Proud of you, statement.") While highly adaptive and psychologically resilient, Rocky also experiences profound grief and survivor's guilt after being the lone survivor of his original 23-member Eridian crew