You may have: Celt or Assassin or Viking or Burgundian.
You may also have something like: "Medieval", which means you could only play these cards during the times that those empires were on the earth (as the above four are).
You may also notice "Legend" as in on the "Oisin the Poet" card.
Legend Cards are people and places from history that have shaky historical support and may or may not have been actual people or places. e.g. Robin Hood.
"Legend" cards are not coming out all at once and Oisin was a Specialty card released on the historical Samhain date, as are most Specialty cards released on actual dates.
Any Epoch or Era Card may be played as long as players agree that they may use them before game commences during deck building.