DragonSlayer Longsword (5e Equipment)
From D&D Wiki
Weapon (Longsword), artifact (requires attunement)
A sword to thick to be considered a regular sword, it is better to consider it to be a raw hunk of iron.
You gain a +3 to your attack and damage rolls.
Damage: 2d10 slashing + 2d8 psychic one-handed, 8d10 slashing + 8d8 two-handed. all damage is considered magical to overcome resistances.
when dealing damage to dragons you deal an extra 2d10 slashing and 1d8 psychic.
when dealing damage to undead you deal an extra 4d8 psychic.
When you attune to this longsword you gain proficiency in intimidation, if you already have proficiency in intimidation than double your proficiency bonus.
Dragonslayer's curse: when you attune to this weapon you cannot use any other weapon in combat because you like this weapon too much.