In the news, the explanations for the new Monster Affixes for Heroes has been added to the Game Guide:
-Arcane - periodically launches an Elemental bolt that purges buffs and creates an aura which increases elemental damage for itself and nearby allies (Found in Grim Dawn: Ashes of Malmouth only)
-Timewarped - periodically unleashes projectiles and fields that slow and petrify and creates an aura which accelerates nearby allies and slow nearby players (Found in Grim Dawn: Ashes of Malmouth only)
-Vampiric - periodically launches a wave of vitality-sapping energy that heals it for the damage dealt and creates an aura that grants life leech to itself and nearby allies (Found in Grim Dawn: Ashes of Malmouth only)
Also, I wanted to list some remaining AoM specific monsters who do not really belong to any of the above groups - often because they are members of monster groups encountered in the main game.
Alya Dugald (Undead, Hero)
I have no idea who the three Dugald siblings are or why their ghosts haunt the Ugdenbog… They are not related to any quest, but they only ever appear once in every playthrough. They spawn in a little clearing right below the middle Riftgate between the Ugdenbog Coven and Barrowholm, if you open a chest. Alya seems to have been a nightblade - she dual-wields weapons and can vanish and use Shadow Strike like Haunted Champions. Like them, she can drop ghost weapon Monster Infrequents.
Bandragos, Thrall of Dravis (Undead, Unique)
A towering Bone Golem, this monster was created and left behind by Dravis, Dalia’s evil brother. You can find it in the middle of the Cinder Wastes. It might be slow, but it has devastating Vitality drain attacks, as well a cold/physical bone wave. Drops the quest item flower and attached little poem that you need to take back to Dalia to complete the quest.
Janaxia, the Betrayer (Human, Unique)
A former Ugdenbog Coven witch, Janaxia fell to the temptations of Ravager. You get the quest from Mallostria at Respected reputation to hunt her down for her crimes. You fight Janaxia in her lair in the Ugdenbog, in a boss room. She has a lot of area spells doing vitality damage.
Janaxia can drop any of three Monster Infrequent daggers that are very useful: the Ugdenbog Chillstrife reduces the resistances lowered by Night’s Chill, the Ugdenbog Flamestrife reduces the target’s damage for Flames of Ignaffar, while the Ugdenbog Stormstrife adds +1 summon limit to Storm Totem.
Neak Dugald (Undead, Hero)
Same with Alya, Neak spawns alongside his siblings near the middle Ugdenbog Riftgate, when you open their chest. He wields a two-handed axe and has Shaman skills, including Lightning spells.
Phris Dugald (Undead, Hero)
Despite the giant axe he wields, Phris seems to be an Arcanist, at least judging by the Trozan Sky Shards that fell on me constantly during the battle. He can be found below the middle Ugdenbog Riftgate, same as his siblings.