Potion, uncommon
One vial of this oil can cover one 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 Freedom of Movement spell for 8 hours.
Alternatively, the oil can be poured on the ground as a Magic action, where it covers a 10-foot square, duplicating the effect of the Grease spell in that area for 8 hours.
This sticky, black unguent is thick and heavy, but it flows quickly when poured.
What is the save DC and what is it based on?
The Grease spell is a 1st-level spell, and the oil’s description does not specify a save DC. However, magical items that replicate spells typically follow the rarity-based save DC guidelines from the 2024 DMG.
According to the table:
A 1st-level spell from an Uncommon item has a Save DC of 13.
Since the oil seems to be Uncommon in rarity, it would likely use DC 13 for its effect when poured on the ground.