The Hooked Shortspear can be found in Out of the Abyss, page 224.
Bound into this weapon is a level 7 spell. The spell is determined when the weapon is created and must belong to the Conjuration, Divination, Evocation, Necromancy, or Transmutation school of magic. The weapon has 6 charges and regains 1d6 expended charges daily at dawn. While holding the weapon, you can expend 1 charge to cast its spell.
The spell's saving throw DC is 18, and its attack bonus is 10.
On a hit with this weapon, the wielder can forgo dealing damage and attempt to trip the target, in which case the target must succeed on a Strength saving throw or fall prone. The DC is 8 + the wielder's Strength modifier + the wielder's proficiency bonus.
A light weapon is small and easy to handle, making it ideal for use when fighting with two weapons.