Bulette Torpedo (Patreon)

Weapon (javelin), very rare (requires attunement)

This javelin is protected by a tough carapace wrought from a slain bulette and can burrow through dirt and unworked stone in order to reach its mark. You gain a +2 bonus to attack and damage rolls made with this magic weapon.

When you make a ranged attack with this javelin, you can throw it into the ground instead. When you do, you can target either a creature you can see or space on the ground within the weapon's range. The space can be a place you can see or one you can describe by stating the distance and direction the javelin would travel through the ground to reach it, such as "100 feet northwest" or "30 feet straight downward." The javelin effortlessly burrows through the ground (if able) to reach the target of the attack, stabbing through the ground at its destination. After the attack, it burrows back to your location, jumping out of the ground and back into your hand. When you roll a 20 on an attack roll made in this way, the target of the attack takes an extra 1d6 bludgeoning plus 1d6 slashing damage as the weapon viciously erupts from the ground, and if the target is a Large or smaller creature, it must also succeed on a DC 16 Strength or Dexterity saving throw (target's choice) or be knocked prone. Attacking a prone creature with this weapon doesn’t impose disadvantage on your ranged attack rolls.

"Oh, I can do a lot with it. It even knows a few tricks, like sit, stay, and stab."