Commander Masters is a Masters set that instead of reprints focusing on multiple formats, focuses exclusively on cards meant for Magic: The Gathering's Commander format. The set features plenty of strong cards from throughout Magic's history. It also included plenty of welcome reprints, with blue receiving some of the best ones.
Blue is one of Commander's strongest colors, and the cards featured in Commander Masters are no exception. These cards push the power level of the format, with some seeing their first reprint since their first printing to allow more players to have access to some of the best blue cards.
10 Mystic Confluence
While not the best reprint, Mystic Confluence is still a fantastic card. It can do a whole lot at instant speed - be it drawing a card, bouncing creatures, or countering a spell. Unlike other counterspells, Mystic Confluence can use excess modes to gain card advantage against opponents if the spell will be countered since three mana can't be paid.
The best blue cards tend to be instant speed, which strengthened Mystic Confluence's other modes to make sure you don't need it for interaction anymore and feel safer casting it for its other effects instead of for its counter effect.
9 Day's Undoing
Day's Undoing is a very good wheel effect that gives everyone a fresh hand. It does cause the turn to end if it's your turn when you cast it (which it most likely will be since it's a sorcery). This doesn't matter too much since you can do it when you're done with your turn anyways. If you have a card that prevents your opponents from drawing extra cards, this can make them lose their entire hand.
In addition, if you have effects that will happen at the start of the end step, Day's Undoing will skip over these as it goes directly to the end step instead.
8 Urza, Lord High Artificer
Urza, Lord High Artificer is one of, if not the strongest mono-blue commander in the whole format. It turns every artifact into a mana rock which can then be used to pay for its effect to cast the top card of your library.
Urza gets out of hand very quickly, especially since its effect is rather easy to pay for. Cheating out spells is one of the best things you can be doing in the format, and Urza, Lord High Artificer is one of the best cards in the game at doing just that.
7 Commandeer
Commandeer has only previously been reprinted in the List, and Commander Masters is the first in-set reprint for it. If a spell has an alternate casting cost, it's usually strong - especially since Commandeer's alternate cost is easy to pay for. All you need is to exile two blue cards to pay for it. Seven mana is a bit costly, but with how much blue can easily draw cards this alternate cost is fairly easy to reach.
This can be worth it as it allows you to steal someone's noncreature spell. This spell could potentially be game-winning, so stealing it can make an opponent's win into yours.
6 Bribery
Bribery had not seen a printing in a set for over a decade, with the last set it was featured in being Eighth Edition in 2003 prior to Commander Masters. The card is easy to cast and is very strong. It lets you steal any opponent's monster directly from their library and put it on your own battlefield.
If an opponent has plenty of strong creatures in their deck, you can take advantage of them before they ever get a chance to play it themselves. Alternatively, you could take their win condition out if they need a specific creature to win, such as a Thassa's Oracle.
5 Capture Of Jingzhou
Extra turn spells are some of the best spells in Magic, especially in Commander. Capture Of Jingzhou is simple, giving you an extra turn spell for just five mana. Commander Masters is its first public reprinting since its original printing in Portal Three Kingdoms.
Capture Of Jingzhou shares an effect and mana cost with both Temporal Manipulation and Time Warp. This allows you to play three cards with the same effect - something normally impossible in Commander as it's a singleton format. This makes Capture Of Jinzhou fantastic paired with these as you have three different ways to take extra turns to make sure you win the game.
4 Personal Tutor
Tutors are some of the best cards in Commander. Since it's a 99-card singleton format, cards that search out for any card add a ton of consistency. Personal Tutor is one that lets you put any sorcery card at the top of your hand.
The downside to Personal Tutor when compared to others is that it's a sorcery itself. However, it only costs one mana and if you have ways to draw cards easily it essentially puts it right into your hand. There are plenty of phenomenal sorceries, making Personal Tutor fantastic.
3 Spellseeker
Some of the best cards in the entire Commander format have a mana value of two or less, and Spellseeker is a way to easily get those into your hand. Although it can only add an instant or sorcery, there is no shortage of strong options. You can even opt to add a tutor to your hand to wind up putting any card you need into your hand.
As a creature, Spellseeker is pretty much just a chump blocker, but the effect is what makes it a star in the format - and almost every deck is better with it included inside the 99 if it can be put into it.
2 Fierce Guardianship
Free spells are among the best kind of spells you can be casting in Commander. Of the cycle of free spells, if you control your commander, Fierce Guardianship is the strongest of the lot. Countering a noncreature spell for free is fantastic, especially when generally more than half of most decks are noncreature spells.
Even without your commander, three mana isn't a large amount of mana to pay to cast it for its normal cost. In addition, catching an opponent casting a powerful spell while you're tapped out can lead to their entire turn crumbling.
1 Cyclonic Rift
Cyclonic Rift is arguably one of the best board wipes ever printed for commander, and it's certainly the best board wipe available in blue. It technically only costs two mana to bounce a nonland permanent, but casting it without paying its overload cast is only a last resort.
What makes Cyclonic Rift so powerful is not only does it only affect everyone else, but it is an instant as well. You can wait to use it until before your turn is about to start to ensure that no one has any battlefield presence, and is forced to rebuild while you get in for damage.