Question: What was the name of the Hebridean rival of the first Kingdom of the Isles ruler known to have died after the year 1000 ?

text: List of rulers of the Kingdom of the Isles
Late 10th and 11th centuries
A posthumous `` Sihtric '' coin from the British Museum , minted at Dublin c. 1050 The preserved remains of the Oseberg ship in the Viking Ship Museum in Oslo 19th-century depiction of Magnus Barefoot 's forces in Ireland .
The Kingdom of the Isles comprised the Hebrides, the islands of the Firth of Clyde and the Isle of Man from the 9th to the 13th centuries AD. The islands were known to the Norse as the Suðreyjar, or Southern Isles as distinct from the Norðreyjar or Northern Isles of Orkney and Shetland. The historical record is incomplete and the kingdom was probably not a continuous entity throughout the entire period. The islands concerned are sometimes referred to as the Kingdom of Mann and the Isles, although only some of the later rulers claimed that title. [Note 1] At times the rulers were independent of external control, although for much of the period they had overlords in Norway, Ireland, England, Scotland or Orkney. At times there also appear to have been competing claims for all or parts of the territory. The islands involved have a total land area of over 8,300 square kilometres (3,205 sq mi)[Note 2] and extend for more than 500 kilometres (310 mi) from north to south. Viking influence in the area commenced in the late 8th century, and whilst there is no doubt that the Uí Ímair dynasty played a prominent role in this early period, the records for the dates and details of the rulers are speculative until the mid-10th century. Hostility between the Kings of the Isles and the rulers of Ireland, and intervention by the crown of Norway (either directly or through their vassals the Earls of Orkney) were recurring themes. Invasion by Magnus Barelegs in the late 11th century resulted in a brief period of direct Norwegian rule over the kingdom, but soon the descendants of Godred Crovan re-asserted a further period of largely independent overlordship. This came to an end with the emergence of Somerled, on whose death in 1164 the kingdom was split in two. Just over a century later the islands became part of the Kingdom of Scotland, following the 1266 Treaty of Perth.
Ruler of the Hebrides and Mann Period of Rule Title Notes
Amlaíb Cuarán c. 941 ? -980 King of the Isles ( and possibly King of Mann ) Amlaíb was later King of Dublin and succeeded Amlaíb mac Gofraid as King of Northumbria in 941 and died on Iona in 981
Maccus mac Arailt 980- ? King of the Isles Said to have been brought under subjection by Edgar the Peaceful , King of England who died in 975
Gofraid mac Arailt ? -989 King of the Isles Brother of Maccus mac Arailt
Gilli 990- ? Jarl Operated under Sigurd the Stout , Earl of Orkney & Mormaer of Caithness . Married to Sigurd 's sister . Sigurd himself was a vassal of the King of Norway
Ragnall mac Gofraid ? -1005 King of the Isles Son of Gofraid mac Arailt
Sigurd the Stout 1005-1014 Earl of Orkney & Mormaer of Caithness Vassal of the King of Norway
Einar Sigurdsson * ? 1014-1016 ? Joint Earl of Orkney Thomson ( 2008 ) suggests Einar rangmunnr may have inherited his father 's territories in the Hebrides
Håkon Eiriksson * 1016-1030 Ruler of the Suðreyar Possibly as a vassal of Cnut the Great
Olaf Sigtryggsson * 1030 ? -1034 King of Mann and many of the other islands of Denmark Son of Sitric Silkbeard and grandson of Amlaíb Cuarán
Thorfinn the Mighty c 1035-c 1058 Earl of Orkney & Mormaer of Caithness Vassal of the King of Norway
Ímar mac Arailt * c 1045 ?  Ruler of Dublin and possibly Mann . In 1045 Ímar crushed the Ulaid in a raid on Rathlin which may be evidence that he also controlled Mann at this point
Echmarcach mac Ragnaill * 1052-1061 King of Mann Probably ruler of both Dublin and Mann prior to 1052 , when he was expelled from the former by Diarmait mac Maíl na mBó . Possibly son of Ragnal mac Gofraid and thus possibly a King of Innse Gall as well
Murchad mac Diarmata * 1061-1070 King of Dublin and Mann ?
Diarmait mac Maíl na mBó 1070-1072 King of Dublin and the Isles Father of Murchad , but who ruled after him over Dublin and , one assumes , Man
Godred Sitricson ? -1074 King of Man
Fingal Godredson 1074- ? King of Man Son of Godred Sitricson
Godred Crovan 1079-1094 King of Dublin and the Isles Son of Harald the Black of Ysland
Possibly Lagmann Godredsson 1095-1098  Eldest son of Godred Crovan . Whether Lagmann began his reign before or after Magnus Barelegs 's arrival is not known for certain