TexasXtreme's 5E SRD
Magic Items O

Weapon (longbow), very rare (requires attunement)

When you nock an arrow on this bow, it whispers in Elvish, “Swift defeat to my enemies.” When you use this weapon to make a ranged attack, you can, as a command phrase, say, “Swift death to you who have wronged me.” The target of your attack becomes your sworn enemy until it dies or until dawn seven days later. You can have only one such sworn enemy at a time. When your sworn enemy dies, you can choose a new one after the next dawn.

When you make a ranged attack roll with this weapon against your sworn enemy, you have advantage on the roll. In addition, your target gains no benefit from cover, other than total cover, and you suffer no disadvantage due to long range. If the attack hits, your sworn enemy takes an extra 3d6 piercing damage.

While your sworn enemy lives, you have disadvantage on attack rolls with all other weapons.

Potion, rare

Beads of this cloudy gray oil form on the outside of its container and quickly evaporate. The oil can cover a Medium or smaller creature, along with the equipment it’s wearing and carrying (one additional vial is required for each size category above Medium). Applying the oil takes 10 minutes. The affected creature then gains the effect of the etherealness spell for 1 hour.

Potion, very rare

This clear, gelatinous oil sparkles with tiny, ultrathin silver shards. The oil can coat one slashing or piercing weapon or up to 5 pieces of slashing or piercing ammunition. Applying the oil takes 1 minute. For 1 hour, the coated item is magical and has a +3 bonus to attack and damage rolls.

Potion, uncommon

This sticky black unguent is thick and heavy in the container, but it flows quickly when poured. The oil can cover a Medium or smaller creature, along with the equipment it’s wearing and carrying (one additional vial is required for each size category above Medium). Applying the oil takes 10 minutes. The affected creature then gains the effect of a freedom of movement spell for 8 hours.

Alternatively, the oil can be poured on the ground as an action, where it covers a 10-foot square, duplicating the effect of the grease spell in that area for 8 hours.