Par and Coll were born and raised in Shady Vale.
Par and Coll had been in Varfleet only a few weeks, using Par's wishsong to make money by retelling the legends of the Ohmsford family, when they are sought out one night by Rimmer Dall and the Federation, who have outlawed the use of magic. They manage to escape the city with the assistance of Padishar Creel and the Free-born.
Par tells Coll of the dreams he has been having, dreams of the Four Lands' demise apparently sent by the shade of the Druid Allanon. Coll tells him the dreams are probably a side effect of Par's use of the magic to retell the old stories of the Ohmsfords, but when they are threatened by a Shadowen one night near Rainbow Lake, Cogline appears. He scares the Shadowen away and tells Par that his dreams were indeed sent by Allanon. Cogline urges Par to go to the Hadeshorn and speak to the shade.
Unlike Par, who is rash and impulsive, Coll is cautious and skeptical by nature, and he tries to dissuade Par from going to the Hadeshorn. Coll was not even supportive of his brother's decision to tell the tales of the Ohmsfords outside Shady Vale, but had accompanied Par to Varfleet anyway in order to keep Par safe.
However, when their friend Morgan Leah takes a trip to Shady Vale and comes back with the news that the Federation has put Par and Coll's parents Jaralan and Mirianna under house arrest, the brothers realize that nowhere is truly safe for them anymore. They decide to go to the Hadeshorn, meeting their relatives Walker Boh and Wren Ohmsford there. However, unlike Par, Walker, and Wren, Coll receives no charge from the shade of Allanon.
Despite receiving no quest from the Druid, Coll accompanies Par to Tyrsis to recover the Sword of Shannara. While Par is engaged with Rimmer Dall, Coll is captured by the Shadowen and replaced with a dopplegänger that Par destroys with his increasingly uncontrollable magic. Par is left devastated and broken, believing that he's killed his own brother.
The real Coll is taken and imprisoned at Southwatch, but is otherwise not treated too badly. During his time there he trains with a Shadowen called Ulfkingroh, growing stronger and fitter by the day. He later escapes by stealing a magic cloak Rimmer Dall had shown him called the Mirrorshroud, unaware that Rimmer Dall had shown it to him on purpose so that Coll would lead him to Par. The Mirrorshroud drives Coll mad in the pursuit of Par, and starts slowly corrupting him into a Shadowen.
Coll finds Par and confronts him briefly before fleeing, unintentionally activating the magic in the Sword of Shannara and causing Par to travel in pursuit of him to Southwatch. When they meet there Coll is able to summon the magic again, freeing himself from the cloak. However, the brothers are separated again during a confrontation with Rimmer Dall, when Coll is transported to safety by the King of the Silver River and Par is left behind because his out-of-control wishsong had prevented the King of the Silver River from reaching him.
Now believing himself to be the destined wielder of the Sword, Coll sets out to save his brother from the torment of his magic and doubt, joining up with Damson Rhee, Morgan Leah, Walker Boh, Rumor the moor cat, and Matty Roh to enter Southwatch. There, Coll uses the Sword's magic to save Par from his own magic.
Coll charges along with the rest of the company further into the depths of Southwatch, but his only magic, the Sword, is useless against the Shadowen. He gives the sword to Par when he is too weak to carry it further, and Par uses it to reveal the secret of Southwatch, which was that it is the location at which the earth is drained of its magic, causing the sickening of the Four Lands. Par frees the earth magic from Southwatch using his wishsong to break the chains holding it captive, and the freed magic eliminates the Shadowen and heals the land.
After their quest, Coll and his brother return to Shady Vale, and later Coll joins his brother and Damson Rhee in opening an inn.
Coll is described as a typical Valeman, a big, strong youth with blunt features, mud-colored hair, and enormous hands and feet, which his brother Par teases him over. Because Par is small and slender compared to Coll and because Coll's demeanor is calmer and more even than Par's, Coll is often thought of as being the older brother, even though he is the younger by two years.
Although the Elven blood had essentially been bred out of the Ohmsfords after generations in Shady Vale, Par and Coll's great-great-grandfather and his son, their great-grandfather, had both married Elven women, reinfusing Elven blood back into the Ohmsford line. However, unlike Par who looks decidedly Elven, Coll has not inherited any of the physical features that give away their ancestry.