WoW Transmog — Browse All Transmog Sets
Browse all 3,100+ World of Warcraft transmog appearance sets. Filter by expansion, armor type (Cloth, Leather, Mail, Plate, Cosmetic), and PvP sets. Track your wardrobe completion across all expansions.
Browse transmog sets from raids, dungeons, PvP, and quests across all expansions. Filter by armor type (plate, mail, leather, cloth) and source. Track which appearances you own and which you still need via Battle.net sync.
Sunless Leathers
Leather set. Dragonflight. Is it normal that I can't transform this with the Renewal Catalyst ? Even though it's the right ilvl ?
Sunless Leathers is a transmog obtainable as a reward from the weekly quest A Worthy Ally: Loamm Niffen.
Complete A Worthy Ally: Loamm Niffen
Complete the weekly quest A Worthy Ally: Loamm Niffen once per week, per character. The quest rewards a treasure bag containing Sunless Leathers along with other items such as 
Lost Dig Map, 
Drake's Shadowflame Crest Fragment, and potentially 
Overflowing Satchel of Coins.
Tips
This quest resets weekly, allowing you to repeat it on multiple characters for additional chances at the transmog.