The Abyssal are a Level 2 class of monsters found in the base set.
Archduke of Pain[]
Official Glossary entry from 1.4 Rules
You must have a Magic Attack of at least +1 in order to defeat the Archduke of Pain. You may still choose to attack the Archduke, even without Magic Attack present. If there are no Cleric and/or Wizard cards in the battle, there is no effect. When the Archduke reaches Rank 1 of the Dungeon Hall, destroy the top two cards from each Hero stack in the Village, including Militia.
Grudgebeast[]
Succubus[]
Official Glossary entry from 1.4 Rules
If you do not have at least +1 Magic Attack, the total Attack Value is halved, round down.
Tormentor[]
Official Glossary entry from 1.4 Rules
If you do not have at least one equipped Weapon in the battle, the total Attack Value is halved, round down. If there are no Cleric cards in the battle, there is no effect. Destroyed Cleric cards remain until the end of the battle.
The Unchained[]
Official Glossary entry from 1.4 Rules
Disease cards gained in battle go directly to your discard pile.