Holy Avenger
Weapon (any sword), legendary, requires attunement by a paladin · 2014 rules, SRD 5.1
+3 attack and damage; extra 2d10 radiant vs fiends and undead; you and allies within 10 ft (30 ft at 17th level) have advantage on saves vs spells and magical effects.
Also in the 2024 rules (SRD 5.2).