In the Mamluk Sultanate there was clearly not only an elaborate interest in the Mongols, but an active exchange of ideas and information between the sultanate and Mongol territories, especially the Ilkhanate. Although many of these exchanges appear to have been through oral informants, it is not always exactly clear how information reached the sultanate. Two Mamluk-era historians—al-ʿUmarī and Ibn Kathīr—appear to have independently used the same (or very similar) version(s) of Juvaynī’s Tārīkh-i Jahāngushā, which contained some conspicuous differences in both content and structure compared to the Persian text as we have it today. From a Mamlukist’s point of view, this is relevant first because it allows for a thorough comparison of al-ʿUmarī’s and Ibn Kathīr’s respective utilizations of the text. Such a comparison reveals their differing intentions in their representation of the Yasa—that vague “something” that was clearly important to the Mongols and in which many Mamluk-era authors took an interest.