A rough guide for the Darkness Sideboard:
vs Mono Devs
-Blitz, -2 Dragons
vs Creature Heavy Bolt/Fractal
-2 Pends, -Blitz
Got to get creatures to stick on board to win.
vs CC Heavy Bolt/Fractal
-2 Pends
vs SoP Squid
Depends a lot on their build. Very difficult match up no matter what we do. If they don't play an early Squid, play creatures. If they do, hope to swarm the board with Blitz + Creature burst.
vs Devtal
-Blitz, -2 Improved Steal, upgrade 2 Pendulums.
vs Grabbow
-Blitz, -Pend, -Dragon.
If they're running a lot of BB/GPull, put the Dragon back in and take out another Pend.
vs Gargoyle Mono
-2 Dragon, -Pend
vs BB Splash
-Blitz, -2 Pend
vs Pandematter Stall
-2 Nightmare, -Fog
Play no creatures, wait for OTK. Make sure they don't have a shield when you need to Blitz.
vs PUgons
-Blitz, -2 Pend
If they're not running many Bolts, you can cut a Dragon and put a Pend back in.