deck is built to take advantage of immortal throne, grosse poltergeist, scavenging fiend, and buried treasure primarily

in order to make throne good, we need to run a really weird curve. ideally, the turn we play throne, we have an untapped seer, so we can instantly tap it to play a land, drawing a card, then follow it up with a 1 drop, drawing another card.

to that end, i figured mix ignis was a good way to make that happen, along with pit vipers. ignis also helps cast big stuff, which is something the deck has issues with, and helps us with cool but expensive sequences, such as seasoned sellsword, pitch undertaker engine -> scavenging fiend. mix makes that a 3 mana endeavor, which is outstanding. vipers help us recover buried treasures and resurface buried or earthquake'd artifacts such as spear of destiny or payload trebuchet, along with letting us safely tuck angels eggs under our sites.

2 drops are pretty easy, we have sellsword, which synergises with scavenging fiend and battlefield, we have a singleton vile imp, and we have far east assassin, which is a SUPER cool little dude. chucking payload trebuchets at people never gets old. most importantly, our 2 drops help us man our trebuchets and move our artifacts around. usually, if our throne turn is as we desire, with throne -> site -> 1 drop, our opponents will play a 2 drop during their turn to try and capitalize on that sweet, sweet card draw, so we often won't even get a chance to play a 2 drop. however, its still nice to have some to help us fill curve neatly and to meet that requirement if our opponent makes us level up the throne ourselves.

3 drops are also pretty easy, as not only are two of our focal cards three drops (poltergeist and buried treasure), but the eggs are also three drops. one of the coolest plays you can do with poltergeist is to animate spear of destiny, allowing it to autonomously fly around and kill surface'd minions. if you want to, you can try out all-terrain vestments, which helps recover buried artifacts and can help the spear survive the void and the subsurface. at some points, i've played mudflow to help quicken the play pattern of buried treasure -> move viper -> move viper -> burrow viper -> surface viper, profit, but i don't like it, and we have better elementless sites, such as gnome hollows, dome of oceiros (protects our poltergeists and trebuchet piles), and great wall.

4 drops include infiltrates, scavenging fiends, chains of prometheus, and i've sometimes ran a single copy of rolling boulder. 4 drops as a whole are pretty popular in multiplayer, so we don't always have to cast a 4 drop ourselves (lots of the best/most fun threats and answers can be found in the 4 drop slot, such as thunderstorm, clamor of harpies, captain baldassare, ruler of thul, pudge butcher, skirmishers of mu, infiltrate, and chaos twister). running as many 4 drops as we are can actually be kind of a risk, because if we, on t5, go throne -> site -> 1 drop, we probably won't have another site in hand, and won't want to draw one next turn. thus, we're likely going to have 5 mana, and therefore aren't able to cleanly play a 4 drop that turn. however, throne can draw sites, and we have access to a lot of solid utility sites, so it's not unrealistic that we want to draw a sixth site to play. plus, a lot of the time we untap with the throne on 4, as after we play our 1 drop, at least one of our next two opponents is more than likely going to have a 2 drop, and one of the last two opponents is likely to have a 3 drop, leaving us to fill the 4 slot.

5 drops include spear of destiny, payload trebuchet, and poison nova. they tend to be enough, though they also tend to be awkward on curve. mix helps, but this is just our most awkward spot on the mana curve. however, you'll often find yourself using seer to help use artifacts such as payload trebuchet, or to recover thrown spears/lost eggs, which sometimes means you just won't play sites after your fifth for a couple turns. if the five drop you're playing is poison nova, this is especially true, as you'll often want to take a step outward to kill more minions with the spell.

6 drops are the worst spot on curve. there just aren't many options period, and most of them suck. purge juggernaut is terrible outside of a hyperfocused water shell (easily dies to attacks, can never attack back, only threatens in a cross shape), so i've stuck with flame wave and pendulum of peril. another benefit of the burrow minions is that they often can hide the turn that you plan on flame waving. (also mix casts flame wave wooo)

7 drops are simple, we've got major explosions, undertaker engine, and death dealer, two of which are castable by mix ignis. undertaker engine is a star performer in the deck, allowing us to easily recover lost buried artifacts that are unable to be carried (LIKE IMMORTAL THRONE, WHICH CONTINUES TO LEVEL UP WHILE UNDERGROUND), to swiftly kill a host of invaders, and to bring up burrow minions holding buried treasures, along with being the best target for scavenger fiend. i would run boneyard, but in multiplayer its hot ass, since it lets everyone bring back a minion.

as for the sites, they're primarily aimed at protecting grosse poltergeist (and us) from attacks while maintaining the fire threshold necessary to cast the aforementioned poltergeist and seasoned sellsword before its too late. mirage is in here because it can return a battlefield to our hand to get the genesis effect again and because it can help you reposition river of flame or vesuvius.

on the topic of a sideboard/maybeboard/budgetboard, rolling boulder is probably the coolest inclusion that i don't have in the deck at the moment. you could swap out chains of prometheus, death dealer, or an infiltrate to include it. another fun maybeboard card is all-terrain vestments. vestments protect your poltergeist from dying to bury, even protecting it by hiding it under the ground from damage-based removal, and give you a way to make a couple more burrow minions to grab treasures and stow eggs. the coolest thing the vestments can do though, is become attached to an animated spear of destiny, allowing it to spear any minion, above/belowground or even in the void, and live to throw itself again. you could run screaming skull to just full on turn an animated spear of destiny into yondu's arrow, but i don't recommend it, because it doesn't have that much utility outside of that specific 2 card combo.