Infernal Rapier is a very rare, moderately enchanted (+2) special variant of the Rapiers family of weapons. It is a martial melee weapon wielded in one hand. As a finesse weapon, it can benefit from the wielder's Dexterity and not just their Strength.
Imagine the soul as a blade. A good one, carefully looked after. A bad one suited for rusting in the rain. Flame-chewed and narrow, this blade is Wyll's soul summarised in steel.
Properties
- Damage
1d8 + 2 (3~10) + Strength or Dexterity modifier 
Piercing damage - Details
Rapiers 
Rarity: Very Rare
Enchantment: + 2
One-Handed
Finesse- Dippable
Melee: 1.5 m / 5 ft
Weight: 0.9 kg / 1.8 lb
Price: 960 gp
Special
The holder of this item gains:
- High Spellcasting: You gain a +1 bonus to Spell Save DC.
- Melee Caster: Instead of its Dexterity Modifier, the affected entity adds its Spellcasting Ability Modifier to Attack Rolls.
- Planar Ally: Cambion: Cast Planar Ally: Cambion once per Long Rest.
Weapon actions
If you have proficiency, equip in main hand to gain:
-
Piercing Strike (
)- Stab an enemy and possibly inflict
Gaping Wounds.
-
Weakening Strike ()- Target an enemy's hands with a non-lethal attack and possibly inflict
Weak Grip.
-
Flourish (
)- Feint an attack to possibly throw your opponent
Off Balance.
Where to find
Potential reward during Wyll's companion quest, The Blade of Frontiers, at the end of Chapter Two. Bring Wyll along when enterring the Mind Flayer Colony, free Zariel's asset, then pass a DC 14 Persuasion Check to successfully ask for a reward.