Use code MARVEL at checkout.
*Offer expires 10/18 at 11:59 PM EST. Promotion code can be used to buy any number of Marvel comics and collections and get an equal number of Marvel comics and collections of equal or lesser value for free. Offer cannot be applied to bundles or preorders.
Not sure how this works with Comixology, but it might unlock the comics in your Comixology account as long as you have it linked to your Marvel account. I know this is the case when redeeming the digital codes within print comics.