There is something truly special in Saviors of Uldum. A card Peter “LegendaryFerret” Whalen has called his favorite Hearthstone card, surpassing Whizbang the Wonderful. A card Chadd “Celestalon” Nervig tweeted is his “favorite card that we’ve ever made.”

The card, the mystery, the legend. Zephrys the Great.

In this article, we’ll explain in detail everything you need to know about Zephrys. Let’s go!

Zephrys is not very self-explanatory. “If your deck has no duplicates, wish for the perfect card.” What is that even supposed to mean?

Zephrys’ Battlecry is actually a Discover effect. It offers you three cards to choose from, and these cards can be any cards from Basic and Classic sets – and from any class, unlike regular Discover. There is, however, one limitation: Zephrys does not offer cards that allow you to replay it, such as Shadowstep and Youthful Brewmaster. If it offered Shadowstep, there would be a rather hilarious OTK with Knife Juggler on turn 4. Yeah, it’s probably for the best that it does not exist.

There is a complicated algorithm behind Zephrys that attempts to determine the best possible cards for your current situation. It looks at several variables, such as your mana, the board state, classes, and how many cards each player has in their hand. However, it does not look at what cards you have in your hand, so if there is a combo you could pull off with cards in your hand, Zephrys does not know about that. The first rule of playing with Zephrys is to work together with it: make plays from your hand first if you want to help Zephrys find a specific card for you.

Zephrys likes to win games, so it will always look for lethal. However, Zephrys is extremely risk-averse. If there is any way to have 100% lethal (remember, it does not check your hand!), Zephrys will give it to you. If there is the smallest chance to fail, it might not. For example:

Zephrys emphasizes cards that you can play immediately. You can affect the cards you are offered by spending or not spending your mana. If you play Zephrys on curve on turn two, it will offer you some good three-drops to play next turn. However, it likes to offer you cards you can play on the current turn whenever possible, and while it often offers at least one card for next turn, cards to play next turn are a lower priority for it. If you are at low health and want to become Lord Jaraxxus, spend some mana first to incentivize Zephrys to look for more cards for next turn.

Zephrys doesn’t understand unique minion effects. If your opponent has a minion with very strong effect (like High Priest Amet, for example) and you want to Silence it, Zephrys most likely won’t offer you a way to do it. That’s because he only sees minion as a pile of stats and recognizes only basic Keywords, such as Taunt, Windfury or Deathrattle. The only exception is Doomsayer, which was added in a recent hotfix – if Doomsayer is on the board, Zephrys should offer you Silence to deal with it. They’ve decided to make it a one-time exception given how popular the card is and how devastating it might be to get the wrong card after already playing him.

Under the hood, Zephrys runs simulations, but it is not a machine learning algorithm. As you learn what Zephrys likes to offer you, you can be confident that this knowledge will remain useful, its preferences will not change.

Overall, Zephrys is a major game changer for Highlander decks. It means that every Highlander deck has potential access to a number of powerful plays on any turn:

The original Reno Jackson only healed you to full health. Zephrys the Great goes far beyond that, the examples above are a mere fraction of its capabilities. That’s why some players are putting Zephrys even in the decks that have no other Highlander synergies, or even run duplicates (to play it after already running out of them).