Successfully complete the indicated task to unlock the corresponding Hero:

Avatan: Win 10 Capture and Hold games.
Berethor: Successfully complete Good Campaign.
Celebrim: Win 10 Resource Race games.
Felek: Win 10 Hero Vs Hero games.
Fhaleen: Win 10 King of the Hill games.
Hadhod: Successfully complete Good Rivendell with all bonus objectives (Level 1 - Good Campaign).
Idrial: Successfully complete Good Dol Guldur with all bonus objectives (Level 8 - Good Campaign).
Krashnak: Successfully complete Evil Lorien with all bonus objectives (Level 1 - Evil Campaign).
Maur: Successfully complete Good Blue Mountains with all bonus objectives (Level 4 - Good Campaign).
Mektar: Successfully complete Good Campaign without a Hero dying.
Ohta: Win 10 Versus games.
Olog: Successfully complete Evil Rivendell with all bonus objectives (Level 8 - Evil Campaign).
Thrugg: Successfully complete Evil Fornost with all bonus objectives (Level 4 - Evil Campaign).
Tumna: Successfully complete Evil Campaign.
Urulooke: Successfully complete Evil Campaign without a Hero dying.