"Only in transmutation, perpetual motion, lies truth" (Asger Jorn)

Of all the tutors out there, Transmute has to be the most confusing.

Huh?

"Give me today, for once, the worst throw of your dice, destiny. Today I transmute everything into gold." (Friedrich Nietzsche)

Transmute allows you to pay a cost (always three mana in some combination) and discard the card to search your Library for a card with equivalent mana value of the card with Transmute, reveal it, and put it into your Hand. (Comp rules 702.53A) The mana color doesn't have to match exactly but quantity must match- if you transmute a two-mana spell, you may get any two-mana spell from your Library, but only a two-mana spell. It exists only in Dimir colors, and hails from Ravnica block, where it is likely to stay, as Wizards doesn't like to print tutors like this anymore.

Let's say you have Dimir House Guard.

At Sorcery speed (Transmute only works as a Sorcery), you can discard Dimir House Guard. It can be countered with Stifle or another activated ability counter, because Transmute is an activated ability (more on that in a minute). Assuming it isn't countered, you get to search your Library for any card with a mana value of 4. You go get Jace, the Mind Sculptor, because why not? You show Jace to the table so they can confirm the mana values match. Jace goes in your Hand, Dimir House Guard goes to your 'yard.

"We are capable of extraordinary self-transmutation and internal self-transformation" (Clive Barker)

It is important to note Transmute only gets that precise mana value. So if you Transmute Grozoth, you can only find a 9-drop. If you Transmute Tolaria West, you can only find a spell with mana value = 0, so another Land or an Ornithopter or something.

On that note, you don't have to find anything... you don't even have to have a legal target. If you want to, you can Transmute, search your Library, and fail to find.

On the other hand, Transmute is an activated ability, and it is an activated ability everywhere. If your Dimir Infiltrator is on the Battlefield, and someone somehow destroys all Creatures with an Activated Ability, your Infiltrator would be destroyed.

Personally, as a Commander player, I prefer seeing cards with Transmute more than Demonic Tutor. At least I can see what the player is up to, and while they surely have a good target, the mana value limitation is a serious one. That said, it's still a tutor, and for some people, that's uncool. Play the spells with care.

Thanks for reading.