This deck plays a lot of permanents with non-tap activated abilities. I didn't want this to be an equipment deck, because I find that quite boring, so instead this deck plays many creatures and non-equipment artifacts with crazy abilities.
Everything below is mainly just me talking to myself while I was building the deck
Just found out that Heartstone reduces the cost for everyone, now I understand why Zirda decks often run Linvala, Keeper of Silence. There are currently only 6 creatures that have an activated ability that can be reduced by 3 (Zirda + Heartstone). Now, Zirda might die, and having a bit of cost reduction is nice, but most of the time Heartstone won't do very much. At 2 mana I might've kept it in, but for now, I'm removing it.
Found out that Gauntlet of Power also benefits your opponents (both tapping and +1/+1). And also, after thinking about it a bit, it isn't even that good for ramping: Let's say it's turn 5 when you play it, let's be generous and say you have 3 mountains. You won't get any mana this turn anymore, but next turn, let's say you play an extra mountain, it adds 4 mana to your mana pool. Later in the game it becomes better, but this is the optimal scenario, in reality, you probably have some non-basics, and some mana rocks instead of all lands. It's basically a bad Hall of Triumph stuck to a bad Gilded Lotus.
Caged Sun is a bit better in that it doesn't benefit your opponents, and the lands don't have to be basic, but it does cost one more. In general though, it has the same problems. If you cast this on turn 6 with 3 mountains, you won't get mana of of it until turn 7 at which point it will add 3 (or 4 if you play another mountain that turn). You might as well play Chromatic Orrery then.
Consider cycling lands, Granitic Titan, Dismantling Wave, Cavalier of Flame, Oketra's Attendant, Quakefoot Cyclops, Sweltering Suns and Akroma's Vengeance. If I decide to add them, also consider Glint-Horn Buccaneer and Unpredictable Cyclone.
You can view Sword of Kaldra as +5/+5 and super-deathtouch. Now the question is, is it worth it? The equiped creatures has to deal damage in order to exile the creature it damaged. Notably, this doesn't have to be combat damage, so Scourge of Kher Ridges (which I was already considering) can basically exile creatures at will.
Cloud Key seems tempting to add, but it might not be as good as you'd think. Since it costs three mana, your mana will be at break-even after casting three spells. But it also takes up a slot in your deck, which is worth at least another mana, maybe two. So this really needs to reduce the cost of 5 spells in order to START generating value. Now at the time of writing there are 28 artifacts and 24 creatures in this deck, so there's plenty of costs to reduce, but you won't always get this turn 3, maybe you get it turn 6, is it even still worth it by that point?
Dismissed Jazal Goldmane because the ability costs a lot of mana, and this deck doesn't go super wide, so the bonus would be quite small.
Dismissed Scourge of Kher Ridges because at 8 mana, it needs to do more.
Dismissed Journeyer's Kite because it's too slow.
Dismissed Rogue's Gloves because this deck doesn't go super wide and doesn't have trample or much evasion.
Dismissed Foriysian Totem because as a ramp card it's too expensive, and too restrictive, and you'd have to be quite desperate to use its second ability.
Dismissed Jayemdae Tome, Seer's Sundial and Tapestry of the Ages because there are better card draw artifacts.
Dismissed Magma Phoenix because it's just a bit mediocre.
Sword of the Paruns is very similar to Glory of Warfare and Dictate of Heliod. Sure you can maybe do some fun tricks with the sword, but Dictate of Heliod just seems better, since the mana cost is the same as casting and equiping the sword (with Zirda out). Because of this, I dismissed it.
Dismissed Crown of Doom. It may look like a 3 mana artifact, but you really need to get rid of it before the end of your turn. Because you can only activate the ability in your turn, opponents can screw you with it too.
MImic Vat needs a critical look. It doesn't work for commanders and tokens, and it's useless for small creatures. You can use the copied creature to attack once or to block once, which can be useful, but I oftentimes you care more about a creature's ability than its power and thoughness.
How does it compare to Mirage Mirror? I think it's most comparable to Feldon of the Third Path, which can target any creature in your graveyard, rather than the most recently killed creature in all graveyards. What I didn't consider is that once you have exiled a good creature to copy, you can do so multiple times, it's not mandatory to always copy the most recently killed creature. This is especially powerful with ETB triggers. But this deck doesn't have many of them.
Do I really want to have an infinite combo in my deck? In play-testing I feel some-what guilty for playing Basalt Monolith, even though this deck doesn't have a card that wins you the game with infinite mana like Walking Ballista. I decided to remove it.
Planar Bridge is quite expensive to cast, and it's ability even more so. Preferably, you'd want to play it and use its ability in the same turn. This would require 12 mana if Zirda is out. It's unlikely this will happen.
This card is basically a tutor and a cheat into play at once, which is undoubtedly strong, however this deck has no game-ending permanents like Omniscience or Eldrazis. If you split the cost into two turns, it will be a big target. If you compare it to a card like Tooth and Nail, which gets TWO creatures instead of one, for 9 mana instead of 12, you start to wonder if Planar Bridge is worth adding. Granted, Planar Bridge is repeatable, but in practice you will only very rarely get more creatures with it than Tooth and Nail.
Thespian's Stage and Mirage Mirror are very good with Dark Depths, but is it worth putting them in for that one combo? Thespian's Stage is not really a wasted slot and Mirage Mirror is also good with many other cards, so yes.
Dismissed Bludgeon Brawl because it takes quite a bit of mana to equip multiple things. On average, Dictate of Heliod will do more mana for mana.
Dismissed Thran Temporal Gateway because there are only three high-cmc artifacts in this deck: Combustible Gearhulk, Soul of New Phyrexia and Clockwork Dragon
Took out Goblin Goliath because 3 goblins aren't exactly interesting, and the damage doubling is done better by Fiendish Duo or Gisela, Blade of Goldnight.
Kurkesh, Onakke Ancient is not worth playing, so I took it out. At the time of writing there are 10 artifacts with non-mana abilities that are not useless to copy. Most of these are card draw abilities. You don't get much value out of it because you pay the same for that card as you would if you activated it again next turn.
Dismissed Nahiri, Storm of Stone because this deck only has 6 equipments, 3 of which equip for free.
Walking Ballista is mostly good if you can generate infinite mana. You can do that with Zirda and Basalt Monolith, however, I'm not a fan of that at all. For non-infinite-combo purposes it's a lot worse than Clockwork Dragon, which gives you 6 counters for 7 mana, instead of 12 mana. Sure, you can cast Walking Ballista for less, but even through the ability the counters are much more expensive.
Dismissed Conduit of Storms
because it doesn't really fit in. It ramps slightly, and it has an ability which can be discounted by Zirda, however, a 2/3 just isn't gonna do much.
Dismissed Endbringer because Zirda cannot reduce diamond mana, the pinging ability isn't useful in this deck, and this deck doesn't have many sources of diamond mana.
After removing Heartstone I can now safely dismiss Linvala, Keeper of Silence.
Dismissed Daretti, Scrap Savant since I'm not a fan of discarding before drawing, and I don't have artifacts I want to sacrifice.
Swords to Plowshares and Path to Exile are arguably better than Chained to the Rocks, however Chained to the Rocks is a lot cooler. I might swap it for On Thin Ice though, which is similarly cool and maybe even a little bit better, because it has more lands to target.
Oketra's Attendant might be a bit sub-par to Kuldotha Phoenix but I still feel like it is good enough to be in the deck.
Removed Umbral Mantle because there are only 4 creatures with tap abilities in this deck, most of which aren't even that abusable.
While Feldon of the Third Path is good when returning creatures with abilities, it's even better to return creatures with enter the battlefield effects. Unfortunately, there are only four of those in this deck. Also, if you have this card in your hand early on, your graveyard will still be empty, so it will just sit there doing nothing.
Dismissed Loyal Unicorn and Rune-Tail, Kitsune Ascendant
because damage is not as big of a deal against big creatures. These cards are stronger in a deck with many small creatures. Iroas, God of Victory has a similar effect, but I'm not dismissing it yet because it also gives creatures menace, which is very useful for big creatures because then they can't chump blocked.
Dismissed Haunted Plate Mail because in many ways it's just a worse Batterskull
Dismissed Gift of Immortality since it is way worse than Hyena Umbra or Felidar Umbra unless enchanted creature has an ETB effect, which this deck has very little of.
Removed Coalition Relic and added Victory Chimes. Most decks can't do much with 1 colorless mana, but this deck has 13 cards with abilities that are reduced to just 1 colorless by Zirda. Occasionally, it can also help opponents deal with another opponent.
Replaced Feldon of the Third Path with Lithoform Engine
Replaced Coldsteel Heart with Mox Opal
Replaced 2 Snow-Covered Mountain and 2 Snow-Covered Plains with War Room, Faceless Haven, Rugged Prairie, and Treasure Vault
Replaced 1 Snow-Covered Mountain and 1 Snow-Covered Plains with Sokenzan, Crucible of Defiance and Eiganjo, Seat of the Empire
Consider Investigator's Journal and Olivia's Attendants and Expedition Map (you can search for non-basics), perhaps instead of Knight of the White Orchid.
Replaced Serum Tank with Oblation
Replaced Oketra's Attendant with Mithril Coat
Consider Master Warcraft, Taunt from the Rampart and Throne of Eldraine and Fabrication Foundry
Replaced Arcane Encyclopedia with Throne of Eldraine
Replaced Boros Signet with Fabrication Foundry because this deck has 30 artifacts so there's plenty to spend it on, so that alone makes it a signet, but the ability to return something from the graveyard (for 1 mana with Zirda out) makes this actually good.
Consider Ertha Jo, Frontier Mentor
Replaced one Snow-Covered Plains with Fomori Vault
