[Taqwus]

Belphegor, Demon Lord, Lord of Corruption is the one with the Corrupt Commander command. It takes pretty heavy Blood Magic to get him.
Pretenders never get blessed; only sacred units, unholy units, Prophets (perma-blessed), or non-pretender commanders with items that confer blessings get Blessed. Blessing gives +3 morale for that battle, plus other benefits possible if pretender was designed with magic >= 4 in any magic path. Except for prophets or commander has blessing items, blessing only actually happens if holy/unholy priest blesses.