Corpse Slayer Whip

1d4 +1 slashing, +1 to attack roll
Finesse, Reach 10
CORPSE SLAYER:
When you hit an undead creature with an attack
using this weapon, the attack deals an extra
1d8 damage of the weapon's type, and the
creature has disadvantage on saving throws
against effects that turn undead until the start of
your next turn.