As of Wuthering Waves Version 1.0, characters who are using Iris as Ascension materials are Calcharo and Taoqi. You can find this at multiple locations, namely Fallen Grave, Lollo Warehouse, Waving Battlefield, and Court of Savantae Ruins in Whining Aix's Mire.
All 48 Iris in Wuthering Waves
First of all, complete the Stygian Lacrimosa Exploration Quest so you can remove the sandstorm at Fallen Grave. But you can only start this quest at Union Level 25. If you don't complete this, you're missing out on lots of Iris.
You can find the first 28 Iris in Whining Aix's Mire. If you didn't complete the quest I mentioned before, then you won't be able to reach the Iris near the sandstorm in Fallen Grave.
For the last 15, you can buy it from Koko in Shifang Pharmacy, Jinzhou. You'll need a total of 45,000 Shell Credits to buy all of them.
