While Orc Drummer is in the staging area, each enemy gets +X . X is the number of players in the game.
Forced: After The Dragon's Thrall engages you, either deal 3 damage to Hrogar's Hill or it makes an immediate attack against you.
Shadow: If this attack destroys a character, deal 3 damage to Hrogar's Hill.
Goblin Eagle-hunter gets +1 hit point per player.
Forced: At the end of the combat phase, deal 1 damage to Wilyador
Shadow: If Wilyador has 10 or less damage on him, deal 2 damage to Wilyador.
Forced: When Goblin Stalker attacks, deal it 1 additional shadow card.
Forced: When Goblin Stalker is dealt a shadow card with 'PASS' printed in its text box, it gets +2 until the end of the phase.
Forced: After Invading Orc attacks and destroys a character, that character's controller returns a location he controls to the staging area.
Shadow: If this attack destroys a character, return a location you control to the staging area.
Forced: After Vigilant Orc enters the staging area, it makes an immediate attack against the first player. If this attack destroys a character, remove 1 time counter from the current quest.
Fierce and shrill rose the yells of the Orcs, and suddenly horn–calls ceased. –The Two Towers
When Revealed: Either reduce each player's threat elimination level by 2, or Orc Seeker engages the first player and makes an immediate attack.
Shadow: Reduce each player's threat elimination level by 2 (5 instead if undefended).
Goblin Prowler gets -30 engagement cost if The Great Goblin is in the victory display.
Forced: When Goblin Prowler engages you, discard a character you control.
...neither Bilbo, nor the dwarves, nor even Gandalf heard them coming. –The Hobbit