Elven Short Spear (5e Equipment)
From D&D Wiki
Forged by the finest Elven smiths, the aptly named short spear is a marvel of both the arcane and craftsmanship. Due to its unique enchanting process, the otherwise one-handed weapon can elongate into a two-handed glaive, becoming a versatile instrument for those who are experienced enough to wield it.
You have a +3 bonus to attack and damage rolls with this magic weapon.
Transformation: By using a bonus action, the wielder can change the weapon from a shortsword into a glaive and vice versa.
Shard of Inevitability:(Optional, Discuss with the DM about this ability) Upon hitting a creature with an attack with this weapon, the wielder may choose to break off the tip of the spear-head into the opponent. The missing shard will quickly "regenerate" itself in the missing space afterwards. At the start of the target creatures turn, they make a DC 16 Strength saving throw to remove the shard. On a failure, the shard will be stuck in the target and will do 1d4 slashing damage to the target. Also, on a failed saving throw, the shard's damage die increases by one, as the magical metal of the spear-head slowly inches further into the enemy's body(1d4 → 1d6 → 1d8 → 1d10 → ect.). If the target fails the saving throw at least 3 times, the shard will continue to be embedded in them and can then only be removed by the remove curse, greater restoration or other similar spells. Outside of battle, the target only takes the damage from the shard every hour until the shard is removed. Should the occupant of this shard be a player, they cannot benefit from a short/long rest due to the dire injury. This property may be used once, and the short spear regains use of this property at dawn.