Spellcasting. The blade is a 9th-level third-caster. Its spellcasting ability is Intelligence (spell save DC 15, +7 to hit with spell attacks). The blade has the following wizard spells prepared:

Cantrips (at will): fire bolt, green-flame blade

1st level (4 slots): shield, magic missile, absorb elements, feather fall

2nd level (2 slots): misty step, warding wind

Blood Frenzy. The blade has advantage on any attack roll against a creature that’s missing any of its hit points.

Bloodstained. Whenever the blade sees a creature, it is automatically hostile to that creature unless that creature was a friend of the blade before they were cursed, in which case the blade must make a DC 18 Wisdom saving throw or become hostile towards that creature.

War Caster. The blade has advantage on Constitution saving throws that it makes to maintain concentration on a spell when it takes damage. It can perform the somatic components of spells even when it has weapons or a shield in one or both hands.

Multiattack. The blade makes two attacks, only one of which may be a Fire Bolt.

Greatsword. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.

Fire Bolt. Ranged Spell Attack: +7 to hit, range 120 ft., one target. Hit: 11 (2d10) fire damage.

Blood Arcana (Recharges on a Short or Long Rest). The blade is overcome by bloodlust, empowering its strikes with supernatural awareness. The first time a creature takes damage from the blade on a turn, that creature must make a DC 15 Constitution saving throw or become stunned until the end of its next turn.

Opportunity Spell. When a hostile creature's movement provokes an opportunity attack from the blade, it can use its reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.