It would be very easy to make this modern if you go trid of your Sol Ring. I Would also cut the Rakdos Signet, then throw in a playset of Lightning Bolt, There was some sort of arcane sorcery that did almost the same thing but its name escapes me,  I would cut the Skull Rend and Chain Reactions, you don't need to kill creatures unless you board it in against an aggro deck, and skull rend is five mana to mess with an opponent and deal them two blightning is far superior. There is also Vexing Devil, and it's not likely to become a creature so congratulations one red for four damage. Now don't forget Skullcrack three to their face right before they start to gain all their life back. More Slagstorm! Hit the pesky aggro decks without sideboard or take both life totals down 3, 5/5 great card.I don't know if it fits with your archetype but Lavaclaw Reaches is a land that finishes people lategame.