The Hooked Shortspear can be found in Out of the Abyss, page 224.
You have a +1 bonus to attack and damage rolls made with this weapon.
When you roll a 20 with this magic weapon, the target takes an extra 7 Piercing damage.
Note: According to the SRD, it is an extra 2d6 Piercing damage, although this is incorrect.
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.