If they could pick literally any religion, why pick one with two gods (Trell and Nalt)? Why risk being caught out when no one follows/believes in Nalt? This has frustrated me to no end. The lack of Nalt is getting my goat up in a pickle.
Also, Trell has got me thinking. In another thread someone said that, in response to a question about Trell, Brandon Sanderson merely left the clue "Rust and Ruin!" Which connects Trell to rust (ruin, obviously, being Ruin). Now my elaborate, possibly outrageously incorrect hypothesis is that Trell is the shard of change. Rust is the change from metal to metal oxide. That way you have preservation keeping things the same, ruin destroying things, and Trell mixing stuff up. The full collection, as it were. And the god metal he creates appears rusty to the observer. You could, alternatively, argue he is the god of decay, but that seems to close to Ruin for me.
Does anyone have any links to some good discussion on Trell? I've been searching hard to find out as much as I can without major success.