Import RSS feed from sub-sites in my multisite from a specific category

hey. I've got multiple sub-sites in my multisite which have their own Authors. I'd like to set up a page which showcases the posts (+featured images) from those sub-sites from a particular category.

So, let's say we've got category 'magazine-category', and it's a common category through a number of sub-sites in the network. I'd like posts made with that category to show up on a page on my main site.

How can this be done?