Talk:Developer's Room/@comment-137.224.220.112-20150126031228/@comment-3211336-20150611202401

To get the Red Stone of Aja, you need to defeat Ultimate Kars, a bonus boss who is in the lake area of Emporio's Sanctuary. You can only find him after you beat Alessi, but he's across the lake from where Steely Dan is.

The item it combines with is the Rusty Sword you get from Utah in Edfu on your 4th (or higher) New Game +.