General thoughts.

[Nightfire107 he/him]

"we have to consider that the timelines in this case likely stretch for millons or perhaps more/less years. The facts are that adulansium shattering made the other shards . But we are still in the dark (i presume) on how one gets a shard and creates life on a planet. Were ati and lerus from another planet and made Scadrial? what about austure? we don't know enough about where the enitial "gods" come from. and brandon has said there is a distinct timeline with i believe liar of partanel( forgive spelling) at the begining. asking him question about timelines would be good. the shadesmere may be unique to roshar as well. we don't know enough about that yet. We need to find out how many shards there are. if some one could compile a "head count" of the shards we could start detirming how many potential planets in the cosmere support shard-holder dieties. Of corse if the shards can go to different planets and create different magic systems that one shard might be two dieties at different times in the cosmere timeline. lots of unorganized thought here sorry."

taken from a post i made on TWG. what do people think?

[Chaos he/him]

As far as I know, the only thing we know about Adonalsium shattering is this: Brandon said that "Hoid was there when Adonalsium was shattered." This, combined with Liar of Partinel sample chapters, where a man named Midius stood over his dead master, Hoid, has led people to believe that Hoid is originally from the world of Dragonsteel.

The epigraphs in Part Two of Way of Kings suggests that they all knew each other once.

How you get a Shard is easy: you pick it up . I don't know. I think its interesting that Preservation had to seek out a particular person to take its power. The MB3 annotations suggest that Vin has some other unique properties. Perhaps these are necessary to take a Shard. I don't really know.

As for Shard count, check out the Shard Total topic. Of the sixteen total Shards, I believe we know of nine of them so far.

[Silus - Shard of Flame he/him]

The thing is about Shards showing up on different worlds as different deities is that Brandon has a tendency to, well, kill them off.  Aona, Skai, Ati, Leras, the Almighty.  That may only be five, but when you're talking about GODS, that's a lot.

Also, our thinking right now is that there are sixteen shards.  With the seventeenth shard (haha) referenced in tWoK Part 2 Epigraphs being a group of people who are aware of the existence of Shards and doing something about it.

[Chaos he/him]

It's pretty clear, if you look at all the epigraphs of Way of Kings, that there are sixteen Shards overall.

"Three of the sixteen ruled, but now the Broken One reigns" being the most pertinent.