Cheapest priced copy (Commander 2014 Oversized): $0.99 at Card Kingdom, foil, near mint, their price list as of .
Teferi, Temporal Archmage 
Legendary Planeswalker — Teferi · Rare · Commander Masters · #125
+1: Look at the top two cards of your library. Put one of them into your hand and the other on the bottom of your library.
−1: Untap up to four target permanents.
−10: You get an emblem with "You may activate loyalty abilities of planeswalkers you control on any player's turn any time you could cast an instant."
Teferi, Temporal Archmage can be your commander.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
5 printings · $0.99 to $3.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2014 | 19 | Mythic | $2.79 | — |
| Commander Masters | 125 | Rare | $2.99 | $3.99 |
| Commander Masters | 500 | Rare | — | — |
| Commander 2014 Oversized | 19 | Mythic | — | $0.99 |
| The List | C14-19 | Mythic | $3.99 | — |
2 rulings from Wizards of the Coast
- 7 November 2014If you control The Chain Veil (from the Magic 2015 core set) and its activated ability has resolved, and you also control Teferi’s emblem, for each planeswalker you control, you can activate one of its loyalty abilities during that turn any time you could cast an instant, and then you may activate a loyalty ability again that turn (choosing the same loyalty ability or a different one) any time you could cast an instant.
- 7 November 2014If you control Teferi’s emblem, the rule that says you can activate a loyalty ability only if none of that permanent’s loyalty abilities have been activated that turn still applies. In other words, you could activate a planeswalker’s loyalty ability once on your turn and once on each of your opponents’ turns.