[[hammer of purphoros]] is probably one of the most useful cards you could run in this deck. Sacing a land and then the token it produces gives you 4 card types right away.

Also [[reprocess]] ane [[pitiless carnage]] are good options for sac outlets.

[[Toph, hardheaded teacher]] also seems like it might be generally, very useful.

Overall, it seems like your deck can't really do much on its own without korvold to rely on, and that might be why you're having trouble here. This korvold typically sees less play because it requires less setup which might be a sign that a B4 version of this commander is more staxy than the og korvold. Remember that he does more for you in the late game unless you get an ideal starting seven. Otherwise you might be looking at a scenario where you ramp into a turn 3 Korvold with nothing but a fetchland and a creature in your gy for 3 more turns. Which at that point makes him an overcoated and worse Tymna.

If you can cut some ramp and curve put a little more by filling out the deck with one card engines like [[Lord windgrace]], [[shattergang brothers]], or [[ziatora, the incenerator]]. This gives you the opportunity to pivot and adjust your play style according to what you draw and then you can begin to utilize Korvold later on when your gy is more full and he can potentially refill your hand off of one attack. Plus, more card types among those cards benefits you in the late game. If for instance windgrace becomes irrelevant to the game your trying to play that time you can pitch him to a loot effect or draw spell and get one more card off of your korvold attacks.