This was done as an extra credit assignment for a class at HOL Virtual Hogwarts (hol.org.uk). The task was to write about a 4th Peverell brother. I’m Zoki Phantom at said site, and this was written in June 2012.
Though Death wasn’t at all interested in his story, to him all that mattered was the fact that these brothers destroyed one of his best sources for taking souls and he was determined to repay them all, one way or another. Therefore he let the little Peverell request a gift just like his brothers did. Grendel had a hard time making his choice, until it finally hit him that he can use the opportunity to further improve his potion-making skills and hopefully finally prove himself in the eyes of his brothers. He asked for seeds that will grow into a unique herb with accommodating properties so that it would be able to substitute any known ingredient in any potion. His brothers laughed at his choice because they thought he could have asked for something much better.
When they finally separated from Death, they all went on their own ways. Grendel settled himself in a small town called Snowlog, located close to the river as he was just too eager to start working with his new herb. He waited patiently as the herb grew up, until it was finally ready for use. He first experimented with it in lower level potions like cure for boils, replacing it for another ingredient, and when he saw that not only did the herb made a perfect substitute but also made the potion stronger, he took his work on a higher level. From love potions to deadly poisonous potions, he created everything and all without the use of any rare ingredients that one could hardly find.
Soon he started his own business which later became one of the best known potions shops, and he himself became a famous potions master. Using the seeds from the grown up herb he managed to plant a whole garden with the same herb by the time his business blossomed. He never had any difficulties in his life ever again, except the fact that being so busy with his potion work he never found love and didn’t have offsprings to continue his work. After his death the garden withered and the shop was taken over by someone else and turned into a book store, covering up any possible trace of Grendel’s history.
However, his legend lived, at least for the people in the town of Snowlog, where the famous sign of the Deathly Hallows now had tiny black dots in the empty space between the cloak and the resurrection stone, representing the magic seeds that Grendel got as a gift from Death.