Omniship is best ship. You know it to be true.
Unfortunately, it seems to be lacking stories on FiMfiction. This group is for displaying all the omniship fics in one place for your viewing pleasure, and to inspire more fics about everyone's favorite OT6.
(For those not familiar with the term, Omniship is the entire mane 6 shipped together)

Please post any omniship fic to one of the subfolders in the All Stories folder, in addition to any other relevant folders.

If you are just looking for general polyamorous shippings, check out the Polyamory group.