Abbot Mordalfus was the mouse successor of Abbot Mortimer at Redwall Abbey. Prior to becoming Abbot, he was called Brother Alf, and was skilled at fishing and served caretaker for the pond. He was a good and trusted friend of Matthias and an old friend of Mortimer.
As abbot, Mordalfus was a very gentle and wise leader, although he had the tendency to trust too much in the goodness of others. He usually had a good sense of priorities and was often the one to advise rest, food and other normal activities in the midst of great turmoil. When Slagar the Cruel took Mattimeo and the other young creatures from the Abbey, Abbot Mordalfus helped restore order and calm among the frantic dwellers.
The Abbot wore spectacles when he was older and often looked above them while talking to younger creatures. A thinker rather than a creature of action, Mordalfus believed in the power of dreams and reflection.
Although he was a creature dedicated to peace, Mordalfus did not hesitate to delegate to other creatures who were better gifted in fighting and deceiving villains. Yet, he knew when to act forcefully and with authority in protecting the other creatures from harm. The ancient Abbot showed great courage and strength when Cornflower, Mrs. Churchmouse and baby Rollo were captured by the magpies and he refused to surrender the Abbey. He even offered himself in sacrifice when the raven General managed to corner the dwellers in Cavern Hole.
As many Abbots, Mordalfus was a great healer and with the help of John Churchmouse, Sister May and Brother Rufus, rescued Stryk Redkite and saved her from her injuries. Abbot Mordalfus was also known to be a great cook and occasionally worked in the Abbey kitchen. He devised 'Redcurrantwall Abbot Alf Cake', and compiled a volume of Mossflower recipes with John Churchmouse.
Despite his position as Abbot, Mordalfus was a fun-loving mouse with a good sense of humor, and a healthy appetite.
As Matthias and his friends were searching the woodlands, the old mouse knew he could also help find the young ones while staying at the Abbey. Mordalfus found the answer from the Spirit of Martin the Warrior while staring at the tapestry. By solving a series of clues, the ancient Abbot and the remaining Abbey dwellers managed to find out where the young ones could be found. Thanks to the help of Queen Warbeak and her warriors, they sent out a map and a set of directions to the search party led by Matthias.
Abbot Mordalfus' fortitude was tested again when the Abbey was occupied by General Ironbeak and his army. Under the Father Abbot's steadfast leadership and with the assistance of Constance, Foremole and the courage and initiative of their friends, the Abbey residents eventually succeeded in defeating the raven and his flock and driving them away from Redwall.
Ever since Mordalfus and Matthias caught a grayling in the pond together, it had become tradition for them to catch a bigger grayling every four seasons.
- In Loamhedge, his name was spelled as Mordalphus.