Cheapest priced copy (The List): $0.35 at Card Kingdom, near mint, their price list as of .
Teferi's Honor Guard 
Creature — Human Knight · 2/2 · Uncommon · Visions · #22
Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)
{U}{U}: This creature phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before you untap during your next untap step.)
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper