From showing his eponymous collection at New York Fashion Week to designing for companies like Starbucks and Payless, Christian Siriano has certainly come a long way since his Project Runway days. And although he partnered with numerous brands before, he's teaming up with Spiegel to launch his first-ever clothing collaboration this spring. "I felt like women really wanted clothes that were glamorous and event-oriented," Siriano told InStyle of the 10-piece occasion collection he created for the retailer. "The women who would be wearing these clothes want to actually do something in them." Siriano said the black cocktail dress, pictured left, was one of his favorite pieces to design. "I really like it because I think it looks organic and fun," he told us. "It's is all draped chiffon—a lot of detail went into making that dress." Siriano's collection for Spiegel, which will feature sizes 2 to 16, will be available on spiegel.com April 4th.