Cheapest priced copy (Duel Decks: Elspeth vs. Tezzeret): $24.99 at Card Kingdom, foil, near mint, their price list as of .
Tezzeret the Seeker 
Legendary Planeswalker — Tezzeret · Mythic · Shards of Alara · #60
+1: Untap up to two target artifacts.
−X: Search your library for an artifact card with mana value X or less, put it onto the battlefield, then shuffle.
−5: Artifacts you control become artifact creatures with base power and toughness 5/5 until end of turn.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
6 printings · $24.99 to $64.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Shards of Alara | 60 | Mythic | $29.99 | $59.99 |
| Duel Decks: Elspeth vs. Tezzeret | 39 | Mythic | — | $24.99 |
| Mythic Edition | WS4 | Mythic | — | $64.99 |
| Modern Masters 2015 | 62 | Mythic | $32.99 | $32.99 |
| Secret Lair Drop | 1111 | Mythic | $44.99 | $57.99 |
| Secret Lair Drop | 1619 | Mythic | $29.99 | $32.99 |
6 rulings from Wizards of the Coast
- 1 October 2008The first ability can target zero, one, or two artifacts. You may activate it with no targets just to put a loyalty counter on Tezzeret.
- 1 October 2008The third ability causes artifacts you control to become creatures in addition to their other card types.
- 1 October 2008The third ability affects all artifacts you control, including artifacts that are already creatures.
- 1 October 2008For the second ability, you choose the value of X when you activate it. You don’t look through your library until the ability resolves. (In other words, you can’t look through your library, decide what artifact card you want, and then determine what X is.) You can’t choose an X that’s greater than the number of loyalty counters on Tezzeret.
- 1 October 2009A noncreature permanent that turns into a creature is subject to the “summoning sickness” rule: It can only attack, and its {T} abilities can only be activated, if its controller has continuously controlled that permanent since the beginning of their most recent turn.
- 1 October 2009The effect from the ability overwrites other effects that set power and/or toughness if and only if those effects existed before the ability resolved. It will not overwrite effects that modify power or toughness (whether from a static ability, counters, or a resolved spell or ability), nor will it overwrite effects that set power and toughness which come into existence after the ability resolves. Effects that switch the creature’s power and toughness are always applied after any other power or toughness changing effects, including this one, regardless of the order in which they are created.