If the blocking creatures toughness is higher than the attacking creatures power, it survives but is damaged
As you can see there are plenty of red and red-leaning cards if you feel like one combat per turn is just not enough
Promos (P) Promotional cards - like the aforementioned Lightning Bolt from MagicFest - can come from events, prereleases, special products, store promos, conventions, Secret Lair drops, and various other places where Wizards know we players are willing to pay top dollar for them
To be honest, there should be another way of getting Lux out as well, though
Consider that Murderous Cut cannot prevent a creature like Siege Rhino from triggering its ability when it enters the battlefield, it cannot kill a Planeswalker, and it cannot stop an instant or sorcery
We still didn't have anything approaching a "set file," but as someone who is more used to designing for Limited, I wanted to test our mechanics in something that felt like the games of Limited I was used to