Cheapest priced copy (Commander Masters): $0.49 at Card Kingdom, near mint, their price list as of .
Surrak, the Hunt Caller 
Legendary Creature — Human Warrior · 5/4 · Rare · Foundations · #768
Formidable — At the beginning of combat on your turn, if creatures you control have total power 8 or greater, target creature you control gains haste until end of turn. (It can attack and {T} no matter when it came under your control.)
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
6 printings · $0.49 to $0.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Masters | 326 | Uncommon | $0.49 | $0.49 |
| Dragons of Tarkir | 210 | Rare | $0.49 | $0.79 |
| Foundations Commander | 232 | Rare | $0.49 | — |
| Foundations | 647 | Rare | $0.49 | — |
| Foundations | 768 | Rare | — | — |
| Dragons of Tarkir Promos | 210s | Rare | — | $0.99 |
3 rulings from Wizards of the Coast
- 25 February 2015Some formidable abilities are activated abilities that require creatures you control to have total power 8 or greater. Once you activate these abilities, it doesn't matter what happens to the total power of creatures you control.
- 25 February 2015Other formidable abilities are triggered abilities with an "intervening 'if'" clause. Such abilities check the total power of creatures you control twice: once at the appropriate time to see if the ability will trigger, and again as the ability tries to resolve. If, at that time, the total power of creatures you control is no longer 8 or greater, the ability will have no effect.
- 25 February 2015If you control a creature with power less than 0, use its actual power when calculating the total power of creatures you control. For example, if you control three creatures with powers 4, 5, and -2, the total power of creatures you control is 7.