Celerum had shared features with the barbarians of the north. He was tall and thin and 6 foot, 2 inches (1.9 meters), with blond hair and blue eyes. He was often dressed in the finest black robes adorned with a jewel-inlaid golden belt.
Celerum was ambitious, arrogant, cold, and calculating. He was completely devoid of morals and would do anything to further his goals. As he had spent significant time impersonating Boswell Peddywinkle, a friendly and outgoing man, Celerum had significant acting abilities.
Under Dendybar's tutelage, Celerum was conducting spell research. He came across excerpts from the diary of Damien Morienus, containing references to a powerful potion, but they did not include a description of the process for making it. Being ambitious, Celerum delved into the archives of the Host Tower of the Arcane, discovering that Damien had a research tower somewhere in Icewind Dale, where he was working on a recipe for lichdom, but mysteriously disappeared before completing it around 1269 DR, a period of the Dale's history called the Great Thaw. Celerum embarked on a quest to discover the accursed tower and the recipe. Celerum traveled throughout Icewind Dale with a friendly merchant, Boswell Peddywinkle. Celerum murdered Peddywinkle along the road and, using his hat of disguise, had assumed the merchant's identity by 1369 DR.