Moonblade

Requires attunement.
You gain a +1 bonus to attack and damage rolls
made with this magic weapon.
Vorpal: Ignore resistance to slashing damage.
When you critically hit a creature, you cut off
one of the creature's heads. A creature may be
immune to this effect, and such a creature
instead takes an extra 6d8 slashing damage.
Thirsty: This item's magic only functions if a
waterskin's worth of fresh blood has been
applied within 24 hours.