In this deck, we're going to abuse Agrus Kos's ability to create mass blink and flicker effects, unholy amounts of ETB damage, and aggressive combos. His text only allows us to copy effects that are attached to permanents' abilities, so most of the blink and flicker in this deck is attached to creatures or enchantments. Nearly every effect in this deck is attached to a creature that can ETB multiple times and accrue value. If something is entering the battlefield, something else is leaving it, and chain reactions are a common occurrance.
The deck's design is to fish out some early game card draw through its cheap creatures, then either burn out your opponents with massive ETB damage or get to one of the deck's combo lines.
Ramp
While Boros relies mainly on artifact ramp there are a few key pieces that get this deck's wheels turning FAST. Springleaf Drum allows you to tap one of your cheap early-game creatures for mana. Meanwhile Solemn Simulacrum or Loyal Warhoundcan fetch you multiple lands if you manage to blink them.
Card Advantage
Who says Boros doesn't draw cards? Card draw in this deck comes in the form of low-cost creatures like Wall of Omens and Spirited Companion that draw you cards on ETB. They provide some advantage early game, and generate a ton of value once you have the resources to start blinking them. Thraben Inspector and Voldaren Epicure also accrue you Clue and Blood Tokens for a rainy day.
Imperial Recruiter and Recruiter of the Guard are the incredibly useful tutors, here to grabbing pieces of your combo. Plus their tutors happen on ETB—which means that if they stick around on the board you can abuse those effects.
I also want to shout out Combustible Gearhulk for becoming one of the scariest cards in this deck. With a damage doubler on the field, he'll make people afraid enough to let you draw cards, and while sometimes he'll swing and miss, his hits can be devastating. The gamble alone is entertaining enough.
The Blink
Felidar Guardian, Restoration Angel, and Icewind Stalwart are the primary flicker effects. card:Teleporation Circle is another solid draw that your commander can copy.
With respect to instants, Cloudshift and Ephemerate are staples, even if Agrus Kos can't copy them. They can get your creatures out of a tough situation, and you can use one of these instants to flicker a creature whose ETB will flicker another creature, triggering your commander, and... yeah anyway you get the idea.
Other blinking permanents include Flickerwisp, Guardian of Ghirapur, and Charming Prince, all of which Agrus Kos can copy.
The Burn
Solphim, Mayhem Dominus is here to make the most of our burn effects. City on Fire is Solphim's scary cousin, and its Convoke ability means that you can get some use out of low-cost creatures while they're on the field.
Terror of the Peaks can be used to impressive effect if you're able to blink creatures once, or even better twice, in a turn.
Demanding Dragon is a great, flexible damage trigger that you can use for board control if need be.
Viashino Pyromancer is modest, but in combination with other effects can become nasty.
Schrodinger's ETB (The 20 Minute Turn)
These are the non-combo win cons of this deck. If the gods are with you, then you start with a late game Dockside Extortionist.
Then, you pull out ETB damage triggers like Impact Tremors, Warstorm Surge, or Purphoros, God of the Forge. If you can fish out your Terror of the Peaks, even better. Ideally at this point you'll have a few low-cost creatures on the field that (alone) don't do much to your opponents.
With three or four cheap creatures and a damage trigger, break out your commander. Then, pull out a Felidar Guardian and a Flickerwisp. Because Flickerwisp blinks creatures back to your field on ETB, they won't go infinite, but they will become disgusting. Your commander allows you to copy these effects to your entire battlefield, meaning that a million creatures will enter at once. Generate lots of clues, blood tokens, or treasures or whatever you have on your field. Destroy things. Generally cause chaos. But once they've re-entered the violence will settle.
When Flickerwisp hits the field, it will also blink your commander, who will blink your entire field, generating more tokens, treasures, and damage. It will ALSO blink that Felidar Guardian, who will re-enter on your endstep and repeat the entire process all over again.
Panharmonicon and Elesh Norn, Mother of Machines will then allow you to double all of these triggers each time you blink a creature.
Bonus points if you can get a Teleportation Circle onto the field, further complicating this mess of exile and leaving your board state in a constant disaster of Schrodinger's ETB damage.
Combo Lines (for if you don't want to take a 20 minute turn)
Impact Tremors combos very nicely with Restoration Angel and Felidar Guardian, allowing you to blink the two creatures back and forth until your opponents die. Notably, this combo can't be tutored easily, so I keep this one in the deck even when I power it down slightly. The commander needs these cards to run, combo or otherwise.
Kiki-Jiki, Mirror Breaker and Felidar Guardian are my go-to combo line, generating infinite token copies of Felidar. Notably, Kiki-Jiki can combo with Restoration Angel and Icewind Stalwart as well, but Felidar can be tutored with Imperial Recruiter.
Board Control
While there are a few staple instants like Path to Exile or a well-timed Blasphemous Act, most of the deck's board control also comes in creature-form. Plundering Barbarian and Loran of the Third Path will allow you to repeatedly remove artifacts and enchantments from the field.
Blink often provides effective protection, so Ghostway and Eerie Interlude function as a value-engine response to someone else's board-wipe.
Exclusions
Conjurer's Closet has a place in this deck, but it's functionally the same as Teleportation Circle, and while I could get a lot of value off of it, I find that this deck does better the more I can attach blink to low-cost creatures and instants, allowing me to blink one creature, who will blink another on ETB, and set off a longer chain. That said, there are versions of this deck I would absolutely run it in, notably in a more casual meta where I tend to remove my most efficient infinite combos.
