> "Stefni eg handseldri sök Unnar Marðardóttur."

'handseld sök' "a suit conducted by proxy". Past participle of the
verb 'handselja' "to make/hand over" (a compound of 'hand' and 'selja'
"give, sell"). -ri is the feminine dative singular ending of the
adjective. MM & HP: "I make this summons in the action assigned to me
by Unn Mord's-daughter."