At the age of nine, Merimas and his family were imprisoned by the Ruffians, led by Bill Ruffin, that invaded the Shire. A month later, Merimas was freed with a number of children and took shelter during the Battle of Bywater. Years later, he attended Bilbo's farewell party on September 12, 3001 3A.
Later, Merimas and his family joined the Shire Company under the leadership of Will Whitfoot when Sauron was preparing to unleash darkness throughout the corners of Middle-earth. He received a Barrow-blade from the Maiar Tom Bombadil and participated in the Battle of Pelennor Fields where he took down a couple of Easterlings that were retreating from the battlefield. After the battle, Merimas volunteered in gathering the wounded and brought them to Minas Tirith to be healed. He later fought in the Battle of Morannon against Sauron's forces and give Frodo a chance to destroy the One Ring. He and Mentha were both slain when they were defending their younger sister.