The Strange Conduit Ring is a great item to pick up as it allows the wearer to deal an extra 1d4 psychic damage with their weapon while they are concentrating on a spell, which should be always for a ranger with hunter's mark. The Cloak of Displacement is a great choice here, making it just that little bit harder to hit them, as it imposes disadvantage to enemy attack rolls against the wearer at the beginning of the wearer's turn each round. While wielding Harold, whenever the ranger deals damage with the crossbow, the target must succeed in a Charisma saving throw or be under the effects of Bane for two turns.