Amurat, Amoroldo, Moraunt, Morholt, Morold, Morolf, Morolt
This Irish knight, the son of King Marhalt, brother of Iseult, brother-in-law (some say son-in-law) of King Anguish, father to two sons named Amoroldo and Golistant, and uncle of La Beale Isoud, was one of the most promising of the first generation of Arthur's knights, playing a substantial role in the early part of Malory's book.
Gawaine and Ywaine, having left the court after Morgan's attack of Arthur and Uriens, found a white shield which Marhaus had left hung to a tree, and twelve damsels defiling it on the grounds that its owner "hateth all ladies and gentlewomen." Marhaus returned, driving the damsels back into their tower and slaying the two knights of that tower in joust; he then recovered the muddied shield, saying, "... for her love that gave me this white shield I shall wear thee."
He now jousted in friendly adventure with Gawaine. Whereas Gawaine's strength increased at noon and then gradually declined until evening, Marhaus became stronger and stronger as evening drew on; thus Marhaus defeated Gawaine. He explained that the twelve damsels who hade defiled this shield were false enchantresses, but "to all good ladies and gentlewomen I owe my service as a knight ought to do." Marhaus swore friendship with Gawaine and Ywaine and the three traveled together until, in Arroy, they met the damsels "Printemps, Été, and Automne". Marhaus chose "Été" and went adventuring with her for a year.
Coming to the castle of the Duke of the South Marches, Marhaus introduced himself - perhaps a little prematurely - as a knight of King Arthur's and member of the Table Round. The Duke had sworn vengeance on that company because of Gawaine's slaying seven of his sons in battle, so he regretfully insisted that Marhaus encountered him and his remaining six sons. Marhaus defeated them all and converted them to Arthur's party.
The damsel brought him next to a tournament cried by the Lady de Vawse, where he "had sometime down forty knights" and so won the prize, a gold circlet worth a thousand besants. Within a week, his damsel brought him to a territory of young Earl Fergus, where Marhaus slew the troublesome giant Taulurd.
On his way back to his year's-end rendezvous with Gawaine and Ywaine, he met and smote down four other knights of Arthur's court, Sagramore le Desirous, Osanna (Ozana), Dodinas le Savage, and Felot of Listinoise. Rejoining Gawaine and Ywaine, he returned with them to Arthur's court where he "was name of the bests knight living" and enrolled in the Round Table at the same time as Sir Pelleas. During Arthur's war with Lucius, Marhaus joined Lancelot, Bors, Kay, and Marrok as one of the King's personal bodyguard. He was among the knights rescued by Lancelot from Sir Turquine.
Unfortunately, when King Mark decided to stop paying his truage to King Anguish of Ireland, Marhaus fought as his brother-in-law's champion. Mark's champion was the newly-knighted, untried Tristram. Marhaus suggested, in kindly fashion, that the young knight abandon a battle he had no apparent hope of winning, but Tristram insisted on fighting.
Thus they fought still more than half a day, and ... Sir Tristram ... [at the last] smote Sir Marhaus upon the helm such a buffet that it went through his helm, and through the coif of steel, and through the brain-pan, and the sword stuck so fast in the helm and his brain-pan that Sir Tristram pulled thrice at his sword or ever he might pull it out from his head; and there Marhaus fell down on his knees, and the edge of Tristram's sword lef in his brain-pan. And suddenly Marhaus rose grovelling, and threw his sword and his shield from him, and so ran to his ships and fled his way ... [to Tristram's shouts of] Ah! Sir Knight of the Round Table, why withdrawest thou thee? ... [R]ather than I should withdraw me from thee, I had rather be hewn in an hundred pieces. Sir Marhaus answered no word but yede his way sore groaning.
Leaving his sword and shield for Tristram to appropriate, Marhaus regained his ship and was taken back to Ireland, where he died, despite all the efforts of Anguish's servants, of the piece of Tristram's sword stuck in his skull. It argues in favor of his great strength that he was able to run away at all and survive as long as he did. He almost had a Pyrrhic victory, however, for he had wounded Tristram with a poisoned spear. In a final twist of irony, when Tristram became a knight of the Round Table, his name appeared on the chair formerly occupied by Marhaus.
Marhaus' behavior in his final battle seems strange - why should such a noble champion have poisoned his spearhead? In other versions of "Tristram", the Irish king's champion is presented as rather less sympathetic figure from the outset. My guess is that Malory either combined the two originally distinct characters or created a nobler early history for Marhaus, but needed the poisoned spear-wound to get Tristram to Ireland, so carried it over from other versions. Or perhaps Marhaus' defeat by Sir Turquine had made him over-cautious. In any case, it is a sign of Malory's stortelling skill and lasting power that he so arranged Tristram's maiden battle as to extend the reader's sympathy to both champions.
Chrétien de Troyes knew some version of the story, without apparently caring much of it, and identified the site of Marhaus' battle with Tristram and Saint Samson's Isle, in which identification the prose "Merlin" and "Tristran" concur.
Gottfried von Strassburg supplies us with the information that Marhaus was a duke (but of where remains a mystery) and Eisner feels that his combat with Tristan was based on that of Theseus and the Minotaur.