Pneuma Blade Longsword (Very Rare)

This blade shouldn't work; the pneumatic seals are made of earwax and leather, the sprockets' teeth are all different sizes, and the structure itself is held together by an adhesive tape decorated with small ducks. The only explanation is that the sheer force of the kobold mechamagicians' belief is encapsulated within this magic sword, allowing it to chomp at its enemies. With a refined pneumatic mechanism, this upgraded version of the pneuma blade is totally, indisputably, and inarguably, 98.4385% guaranteed not to backfire. The new-fangled heating element is also almost absolutely perfect.

Pneumatic Strike: After you make an attack roll with this weapon, but before the result of the attack is determined, you can use a bonus action to pull the blade's trigger. With a pneumatic thrust, the top of the weapon arcs forward and you gain a +5 bonus to the attack roll.

Heated Weapon: When you hit a creature with an attack that uses Pneumatic Strike, the pathogens that live within the rusty blade are reinvigorated by its magic, and the attack deals an additional 2d8 fire damage.

Burnout: When you use the Heated Weapon property of this weapon and roll an 8 on both of the additional fire damage dice, the heating mechanism backfires. Each creature within 10 feet of you (including you) must succeed on a DC 16 Dexterity saving throw or take 4d6 fire damage as scalding pneumatic fluid bursts out.

Versatile: This weapon can be used with one or two hands. A damage value in parentheses appears with the property—the damage when the weapon is used with two hands to make a melee attack.

Proficiency: martial, longsword Source: Heliana's Guide to Monster Hunting - Part One p. 487, Player's Handbook (2014) p. 149