All of the Shards that we have seen so far have been invested in a Planetary Sphere to at least some degree, apart from one big player.
The big O.
Odium has moved between systems destroying a number of shards, after splintering Devotion and Dominion on Sel he moved to Roshar where he facilitated the destruction of Ashyn and gave Honor and Cultivation time to set up a plan, I believe the plan involved bogging down Odium in a prolonged conflict forcing him to Invest on the nearby sphere Braize, he was then bound there by the Oathpact, his influence on Roshar limited and his escape from the system prevented.
The importance of a shards relation to their Sphere has been underrated so far in my opinion, have nothing to back it up as there is very little info regarding interstellar shardic or other wise travel yet just a feeling
The plan came not without cost and binding Odium to Braize killed Honor... we still don't really know or understand how Honor was killed, he existed during a number of desolations seemingly went mad and then suddenly met his demise post final desolation I believe? (correct me if I'm wrong there)
anyway been a long time reader here (usually while at work ><) first post, its been a quiet day let me know what you guys think