The relative pronouns in Old English are þe and se, þe being used when the clause has the function of a limiting or distinguishing adjective and se when it has the function of a descriptive adjective, e.g.:
Se casere þe wæs Claudius haten ‘the Emperor called Claudius’.
Se casere, se wæs Claudius haten ‘the Emperor, who was called Claudius’.
In the first sentence the relative clause distinguishes one particular emperor from others, in the second it adds a descriptive detail to a noun already sufficiently defined. Both kinds of clause may qualify the same noun, e.g.: Hom. I. 100.4 Se eahtateoða dæg þæs monðes þe we hatað Martius þone ge hatað Hlyda ‘the 18th day of the month that we call March, which you call Hlyda’. The analogy of other subordinate clauses leads us to expect that conjunctive order will be the rule in the relative clause, and this we find to be the case; but common order is a frequent exception especially when the verb is unstressed, e.g., ‘sum mæsse-preost on þam lande þe is gehaten Hispania se wæs ðearle geswenct’. Occasionally the order of subject and verb is inverted as in ‘Abel þone ofsloh Cain his broðor’.