Tiny Epic Dungeons

If the Boss leaves its Lair and then comes back there, can I attack the Boss from outside the Lair?

If you move the Boss back to the Boss Mat, in order to attack the Boss you must move from the Lair Door Card to the Boss mat. While a Boss is in its Lair, heroes outside cannot use any attacks, including Missile or Spell Attacks, against it. All your attacks must be done while on the Boss Mat.