While the core of D&T is pretty solid, there are always going to be a handful of “flex slot” choices for your maindeck creatures. The flex slots that you play can (and should) change frequently as the metagame shifts. This page is a brief explanation of some of the strengths and weaknesses of your flex cards. This is not meant to be an exhaustive primer on each creature, but an “at a glace” at the best times to play various flex slots. This page only considers options for the mono white builds.
Mirran Crusader
Crusader is one of the best generic beaters. It is also our swiftest clock when paired with equipment. It also serves as a “hate bear” for the various green and/or black decks of the format. It is particularly difficult to remove for those decks. Crusader is weakest when the metagame is full of red and white removal. Crusader is strongest when the metagame is focused around black removal.
Serra Avenger
Avenger is not really an impressive looking card on paper, but it is much stronger than it looks. This is primarily because it can come off of Vial as an extremely aggressive threat. Its evasion is its best trait, so this card is best in metagames where ground-based board stalls are common. It’s very poor in the face of Baleful Strix though.
Brightling
Brightling is an insanely powerful Magic card. It has a degree of flexibility not seen in perhaps any other card in our deck other than Flickerwisp. It is a nightmare for control decks, especially Miracles. It is nearly impossible to answer if you have the mana to protect it, and it can do disgusting things with Vial. It provides a great source of life gain against tempo decks like RUG Delver, and it also closes the game surprisingly quickly. It has a few other quirks like being able to sneak under an Ensnaring Bridge as well. That being said, it lines up poorly against black creatures like Baleful Strix and Gurmag Angler.
Palace Jailer
Palace Jailer is a high risk, high reward card. It wins someone the game…but it isn’t always you! Against decks that rely on one or two creatures, this can really push you far ahead. If your opponent can take the crown though, perhaps with creatures like Baleful Strix or True-Name Nemesis, you are in trouble. This card is best when you can play it and remove your opponent’s only creature, and worst when your opponent has expendable and/or evasive creatures that can easily take the Monarch status.
Spirit of the Labyrinth
This card hoses blue cantrip-based decks, but dies to…everything. Spirit doesn’t handle combat well on either offense or defense, so it’s best vs combo decks, especially those that can’t play Dread of Night. It’s also great against decks that rely on drawing cards as a core part of their strategy (e.g. Elves).
Sanctum Prelate
This card will single handedly lock out many decks of the format if played at the right time. Many decks fold to Prelate on a certain number and have literal zero game one answers to it. That being said, it is a touch slow compared to other hate cards. It tends to be best against decks with a low diversity of converted mana costs of removal spells or with most of their win conditions centered around one converted mana cost. It’s at its worst against decks where you want to put it on one but also need to cast your own one drops (e.g. vs Delver decks).
Thalia, Heretic Cathar
Thalia 2.0 is powerful against the right decks, but generally speaking a little too slow for this deck. It’s much better played on turn 2 in a deck like Maverick. That being said, it is a house against decks like Elves, Maverick, and Eldrazi; these decks rely both on creatures and lands entering untapped as an essential part of their gameplan. The taxation is most noticeable on fetchlands and haste creatures. Thalia 2.0 is terrible on the draw and against decks that aren’t playing creatures and/or have lots of basic lands.
Mangara of Corondor
Mangara is “sweet.” It’s a card with high potential for abuse, and it can dig you out of some crazy situations. That being said, it is slow and requires multiple other cards to be good (ideally Karakas and a Vial at 3). Mangara is best against slow, removal-light decks. Unfortunately, there aren’t too many of those floating around right now as compared to Mangara’s peak a few years ago. It is worst against decks like Grixis Control that are saturated with removal and against extremely fast combo decks.
Remorseful Cleric
Remorseful Cleric is a really good maindeck option when graveyard decks are popular. It’s an aggressive body as well, and trading with a Delver is a pretty big deal at that cmc. It is at its worst in formats where Dread of Night is a popular sideboard card. It will be at its best against midrange or slower graveyard decks like Dredge, Lands, and 4c Loam.
Aven Mindcensor and Leonin Arbiter
These cards are “soft hate” cards. They can be played around to a certain extent, and they are high variance cards in terms of their potency. Generally speaking, these cards are not good enough for the Legacy version of the deck. That being said, some people do try to pair them with Ghost Quarter to play additional “Wastelands.” These cards tend to increase your power in the early game, at the cost of your late game. These cards are much better on the play as well.
Eldrazi Displacer
This card has the power to do some silly things, but is very mana intensive and slow. It’s the sort of card that isn’t great if you shove it in your deck, but can be very powerful if you build around it. If you are exploring a build with Ancient Tomb or with multiple additional creatures with enter the battlefield triggers, this card is worth exploring. It is best against opposing decks that rely on a single creature (e.g. Infect, Reanimator).
Vryn Wingmare
This card stacks with itself and with Thalia. This can be extremely potent against most decks in the format that rely on fixing with cantrips. In particular, this taxes the blue-based combo decks the hardest. Vryn Wingmare tends to be a powerful game 1 card, but loses some oomph in the post-sideboard matches. The deciding factor about when to play Wingmare is often how much hate is in the sideboard for D&T. When Dread of Night and friends are popular, leave this at home.
Brimaz, King of Oreskos
Brimaz is a powerful threat than can be protected by Karakas. It’s not exactly an army in a can, but it can protect itself from an edict effect if it makes it around the board once. It shines against non-black control decks, especially Miracles. It’s also a great threat when red removal is the dominant removal of the format. It’s a little embarrassing in the face of a Baleful Strix though.
Restoration Angel
Restoration Angel is essentially your 5th Flickerwisp. The body is bigger, but it is a touch less flexible and slower to hit play. It is at its best in a slow, midrange format. It dodges some common removal like Bolt and Abrupt Decay while also offering value by saving your creatures from removal or reusing an enter the battlefield trigger. This creature is basically unplayable when combo decks are prevalent, as it is too slow.
Shalai, Voice of Plenty
Shalai is Mom #5 while also being a real threat. Its primary utility is to protect your other creatures, but it does occasionally hose some combo strategies as well. Shalai, like Restoration Angel dodges lots of common removal, but it also stops edict effects too! One of Shalai’s other liabilities is that it is legendary, so don’t play this when Karakas is common; it feels terrible to invest four mana in something only to have it bounced. Shalai is probably at its best in a slow to midrange format that is light on Karakas.
Hallowed Spiritkeeper
This is a card with huge potential against control decks. As the games go extremely long, this card has the potential to turn into a threat that cannot be blocked out of fear of the token army that would follow. This card is best in a metagame full of slow non-white decks, where the token army provides some degree of end game inevitability. This card also pairs well with cards like Honor of the Pure or Gideon, Alley of Zendikar; while 1/1 tokens are great, 2/2 tokens just feel dirty! This card performs poorly against white removal and against any fast decks.
Walking Ballista
Walking Ballista recently has started to see play in sideboards and is now starting to trickle into the maindeck. While it doesn’t pair well with Vial, it does have the possibility of taking over certain matchups. It can dominate the mirror, removing the otherwise problematic Mother of Runes and decimating the rest of the creatures as well. It’s a decent threat against control decks, where you can cast it for large numbers in the late game or pick off their smaller threats like Snapcaster Mage and Baleful Strix. It will be unplayable vs combo decks, as it is just too slow of a threat.