Most dates during the Norse period are approximate, but records become more detailed and historically accurate as the line of Norse jarls comes to an end. After the close of the Jarls' Saga on the death of Jon Haraldsson in 1230, the history of Caithness is "plunged into a darkness which is illuminated by very few written sources". After the rule of Maol Íosa there was no mormaer of Caithness from c. 1350 to 1379. The title Earl of Caithness was granted to David Stewart, a younger son of the Scots king, and the mormaerdom effectively continued as an earldom from that point onwards. Mormaers of Caithness The list is by necessity a fragmentary one, the archives being not fully preserved, the reigns of some supposed mormaers being not fully attested, and so forth. According to the Landnámabók, Thorstein Olafsson (fl c. 850-c. 880) and Sigurd Eysteinsson “conquered Caithness, Sutherland and Moray, and more than half of Argyll [and] Thorstein ruled over these territories as King”. There is no suggestion that Thorstein was beholden to any overlord although his son-in-law Donnchad is described as a "native earl". Norwegian interlude In 1098 Magnus Barefoot, King of Norway deposed the Thorfinnsson brothers as Earls of Orkney and set his 8 year old son Sigurd Magnusson up in their place. This was an unprecedented occurrence, probably intended as a permanent step. Magnus then conducted two vigorous campaigns in the Hebrides and Irish Sea region. It is likely that de facto control of the mormaerdom was in his hands prior to his death during the second campaign in 1103 although "there does not seem to have been any intention on the Norwegian side" to formally take control of Caithness, which remained subject to the Scottish crown. It is possible the native Celts regained the title at this time. in the late 11th or early 12th century, Ótarr son of Madadhan and brother-in-law of Haakon Paulsson is described as "jarl of Thurso". It is not certain that this second "Moddan of Dale" was a descendant of his earlier namesake, and there is no suggestion that Moddan himself was a jarl. Ótarr was the brother of Helga Moddansdóttir fl. 1015-23 and a "curiously shadowy figure". Later Norse jarls After the failure of Harald the Younger, c.1200 William of Scotland then asked King of the Isles Rognvaldr Gudrodsson (Raghnall mac Gofraidh) to take Caithness on behalf of