He was a member of the Folkung dynasty, which in the 1250s became Sweden's royal dynasty. He was the son of Magnus Minniskiöld, and the elder brother of Birger Jarl, one of the most powerful men of his time in Scandinavia.
Around 1217, he married Kristina Nilsdotter, the widow of the Norwegian earl Hakon the Mad (d. 1214), whose son Knut was a pretender to the Norwegian throne. Due to the location of his jurisdiction and his marriage to Kristina, Eskil had good contacts in Norway and often functioned as a negotiator between the Swedish and the Norwegian government. In 1218, he was visited by his Icelandic writer and politician Snorri Sturluson.
Eskil was noted for his learning and seems to have had an important role in codifying the Västgötalagen or law of Västergötland, the oldest known Swedish text written in the Latin script. An old list of the lawspeakers of Västergötland tells that he collected and edited the province's laws, and administered justice with great consideration. He had good judgment, the learning of a cleric and he was superior to all the chiefains of the kingdom. He also distinguished himself in bravery and the list claims that it would take a long time until another man of that kind was born.
- Inger Larsson, 'The Role of the Swedish Lawman in the Spread of Lay Literacy', in Along the Oral-Written Continuum: Types of Texts, Relations and the Implications, ed. by Slavica Ranković, Leidulf Melve, and Else Mundal, Utrecht Studies in Medieval Literacy, 20 (Turnhout: Brepols, 2010), pp. 411-27 (pp. 411-13).