Yo, I don't know how this thread managed to slip under my radar, but all of these ideas are really
ing cool. Especially the Monsoon, which brings the North Pole/Cursed Dart effect to pre-Hardmode.
Though there are a couple of questions I'd like the answer to:
-Currently, sand is technically a renewable resource, but only through extremely weird methods like camping near Antlions, or using the Sandgun with ammo conservation bonuses. I see a lot of recipes that require sand, but in the end, sand remains nonrenewable; changing the Sandgun so it no longer creates a mess would be essential to make it a practical weapon, but that comes with the side effect of making sand even harder to farm than before. I know that it's available in large quantities, but generally I believe that consumable resources should be renewable, no matter how abundant they are at first.
-I saw "cloud of damaging sand" or something to that effect several times. Now for the Sandgun, sure, that's fine. But for a sword, I'm sure you can come up with something better. Right now I'm imagining it kind of like the Chlorophyte Saber, which is a weapon that I don't consider to be very good. And the bullets are looking disproportionately powerful for preHM; I know that you haven't included an exact number, but with such a strong attack pattern, I don't see how it could be brought in line with the other preHM bullets without gutting its damage entirely.
Basically, look at all the concepts that "create a cloud of damaging sand", and choose one.
-I sure hope Sunstone is a status effect applied to a block and not a complete override of the block's identity, because a boss that can actually edit blocks is going to potentially cause problems. Even that box that the Wall of Flesh creates upon death is starting to look a little dated.