The cards in this category represent creatures with powerful etb/ltb/death effects that can be abused in combination with an enabler. Some possibilities for roles they could serve are: removal, draw, ramp, recursion, and many more.
Archon of Justice - One of our most powerful removal effects, when paired with an enabler this can make sure that the board stays clear of any threats. It is especially effective at dealing with graveyard-based strategies, since it exiles the permanent, making sure it stays gone.
Aurelia, the Warleader - This is kind of a weird card in the deck, since it doesn't generate much value per-say, but when paired with an enabler can give you one or more extra combat steps every turn. It is notable for also untapping Brion when she attacks, letting you loop her many times given a suitable amount of mana and the correct enabler.
Burnished Hart - Not only can this get your mana production started in the early game, if you can loop it you can help set up a vast mana base to set up a powerful combo turn.
Cataclysmic Gearhulk - I really like this card as a powerful and easily recurable board wipe. However, with recent changes to the deck, it could interfere with all the equipments I run, so while a very powerful creature, it might not have a place in the deck anymore.
Combustible Gearhulk - There are a bunch of fairly high cost cards in this deck, so opponents might be hesitant to take the mill option, and even if they do there's a pretty good amount of recursion in the deck. Looping this and choosing the same player each time should eventually get them to give you cards, and any draw is very nice in a boros deck.
Duergar Hedge-Mage - I really like this card in here, since it can hit lots of very relevant cards, and even if there's nothing that threatening on the table, you can loop it to blow up people's mana rocks.
Godo, Bandit Warlord - This card has lots of options for what it can fetch. Usually you want to go for draw, but if you have the mana to do so, it could be good to first get an enabler to help you loop Godo. This is part of what makes Godo and some of our other tutors very powerful, they can find an enabler, serving as a one card value engine.
Hoarding Dragon - This can find a few more important pieces than Godo, but has the disadvantage of needing to die to actually give you access to the tutor target. This means that it's harder to use it as its own enabler, but the additional cards that you can tutor with it makes it well worth the slight inconvenience.
Humble Defector - I like to pass this card around the table in the early game, and then transition into using it selfishly, sacrificing it in response to its ability to stop my opponents from getting it. While this is slightly harder to abuse (it needs haste or for you to wait a turn to activate its ability), card draw is one of the hardest roles to fill in this deck, so I'll take what I can get.
Karmic Guide - This card is hard to take full advantage of (echo trigger can force you to spend lots of mana so you can set up an enabler, and it's limited by your graveyard), but can generate incredible value, letting you recur your powerful creatures.
Knight of the White Orchid - Looping this isn't all that useful, but it's a good ramp tool in the early game. This gains a lot of value if you can afford dual lands, since in that case it also serves as mana fixing. As is, this is pretty decent because it can fetch Mistveil Plains, a very powerful utility land in this deck.
Molten Primordial - I'm unsure that this is strong enough in the deck in its current form, since it requires additional sacrifice outlets or a way to untap Brion in order to sacrifice all of the creatures it steals, but I like having another way to steal creatures in the deck. It's also hard to loop this while still having access to Brion as a sacrifice outlet, so it's definitely one of the less abusable value creatures in here.
Solemn Simulacrum - This ramps you and draws cards, basically everything we want to be doing to set up for our late game. Definitely an incredibly powerful card to loop.
Sun Titan - This doesn't even need an enabler to generate repeated value, which makes it very powerful. With a free sacrifice outlet (which the deck currently does not include), it can go infinite with various cards. Even without these combos, this is still an incredibly powerful value engine, ramping you in combination with fetchlands, drawing cards with Mind Stone, or just getting back useful equipments.
Thalia's Lancers - I just added this card to the deck recently, but I'm very impressed with what it can do. It can fetch any equipment through Godo, Bandit Warlord, fetch a big mana producer in Neheb, the Eternal, or even find an enabler in Kiki-Jiki, Mirror Breaker. Basically, this is probably the best tutor in the entire deck.
Treasure Keeper - A lot of our powerful utility cards have cmc<=3, so looping this basically just helps you find combo pieces for the late game. Much like Solemn Simulacrum, looping this is pretty much everything we want to be doing.
Zealous Conscripts - Stealing planeswalkers to ult them, stealing creatures to fling at people, untapping Brion to continue a sacrifice chain. Basically, this card does it all. Oh, and did I mention that it also is half of one of the easiest combos in the deck? This card is an all star.
