Haven't played for several years, but if you have Nevinyrral's Disk, I'm guessing this is Vintage or Legacy? You have multiples of stuff other than basic lands (and less than 100), so can't be Commander...
Not familiar with the current meta, and this is my first time seeing many of those cards, so take my thoughts with a grain of salt.
Looks like your main win condition is laying out (ideally) multiple Reckoners and Spritmares, pumping RR into Pyrohemia every turn (yours and opponents) before the end step (as long as it wouldn't kill off your reflectors), and/or dropping a Blasphemous Act to reflect the damage to your opponent?
If so, would there be value in running
four of those creatures to increase your chances of drawing/dropping them, replacing them if they die blocking (which also reflects damage on your opponent or kills off one of their threats), and to have more in play to reduce the cost of Blasphemous Act? Not only do they help you win, but they're also one of your best sources of defense from creature damage. Though neither of them fly...
Any value in dropping one or two Magma Jets either for additional reflect creatures or an additional Browbeat (which seems great in this deck)?
Pyrohemia is obviously huge and you want to get it up and running ASAP, but unless you find yourself losing them with no creatures out frequently, could you drop down to 3? Note the ruling for it:
Note that “until end of turn� effects wear off after “at the beginning of the end step� triggered abilities, so an artifact that animates until end of turn can keep this on the battlefield.
What are those lands that you can temporarily turn into creatures? Mishra's Factory or something like that? If necessary, animate one just before the end step to keep Pyrohemia up?
Sun Droplet is going to work well with Pyrohemia - healing much of the damage you do to yourself. But unless there's an interaction I'm missing (which is entirely possible - I'm tired, and haven't played in years) it doesn't seem strong enough to run four of. An extra Bolt, fourth copy of the reflector creatures, an extra Smoke... all seem better. It's at most 2 points of healing each round (one on your turn, one on your opponent's, right?) But I may be missing something.
Smoke is a great one here. Hell, replace four Mountains with Volcanic Islands and run a couple copies of Stasis as well. Or not, because at best you'd only be able to keep it running for three turns, and Stasis would prevent you from untapping Mountains to fuel Pyrohemia. Yeah. Ignore me.
What about a
Blood Moon in the main deck or sideboard? You're completely immune to it, but chances are your opponent is not.
Blood Moon would turn a
Mishra's Factory into a Mountain if you had both in play, but no big deal. Factory is useful to you as a source of colorless mana that can also turn into a temporary 2/2, but it's also useful to you as a basic Mountain if you drop Blood Moon.
I was going to suggest
Mana Flare, but while you could probably pump another R into Pyrohemia in response to your own previous activation of it before the previous activation resolved, that doesn't matter... the third activation that finally resolves will kill off your reflectors, and any additional activations waiting on the stack won't be duplicated and reflected by your characters, right? Unless one more point of damage would finish off your opponent (or one of their threat creatures), you'd never want to feed more than RR into Pyrohemia in a given turn, right?