Hello, and welcome to the September update to my sideboard guide for UR Murktide. As always, I like to start with my current recommended decklist:

You can find a downloadable copy of the decklist here.
 
Note: I haven’t had that much time to play after the Dominaria’s release, and while I like the build I posted above, I haven’t tried DRC which I think might actually be in the best spot it’s been for a while. I don’t want the full four almost certainly, but with maindeck Blood Moons and Creativity/other decks you’d like to clock, I can see trimming Charms that aren’t that easy to cast under the Blood Moon and add two copies or so of Darcy (maybe alongside second maindeck Snapcaster Mage to get a bit more punching power without Charms, although there’s a good chance it can stay in the sideboard instead). Force of Negation is another card that I’m yet to try in this deck and I like in theory, especially in conjunction with Blood Moon since it allows you to get this 1-2 punch of Blo...