 Thomson (2008) identifies the joint rulership of earls as the key recurring theme of the "Orkneyinga Saga" in the period up to 1214.The initial friendship between Paul and Erlend Thorfinnsson notwithstanding, this was a situation that was "inherently unstable and usually ended in violence".These family feuds culminate in the martyrdom of Magnus Erlendsson c.1115, and Thompson believes that the Icelandic writer is emphasising the doom of "kin-slaying".