Adrip with Kereska's Acid Affected entity has Resistance to Acid damage. Your acid spells deal additional Acid damage equal to your Proficiency Bonus. When it deals spell damage, inflict 1 turn of Noxious Fumes upon the target. While attuned to Kereska's acid it can cast Melf's Acid Arrow and Hunger of Hadar.
Sources of Adrip with Kereska's Acid
Notes
* As of 08-08-2023, the in-game tooltip is incorrect and states this variant grants the spells granted by Deadlier than Arsenic instead. * As of v4.1.1.3956130, dealing spell damage applies 3 turns of Noxious Fumes instead of 1 as stated in the tooltip.