In the basic game, in its Vassal and Tabletop Simulator version, are provided the standard and ready to use Monsters Decks (Wandering Monsters and Dens Cards), already properly composed: each Dungeon indicates on the Objective Card which Decks are used and if/how they have to be combined and modified. The composition of the standard Monsters Decks is the following, divided in Wandering Monsters Cards and Dens Cards
The Monsters Addons published add their own Wandering/Dens Decks already composed, but anyone can customized a Monster Deck and even create new Monsters to add in custom encounters. AHQ3.0 is, anyway, a game based on the balance, on the Heroes mortality but at the same time on the absence of Dungeons inhabited by unbeatable and invulnerable creatures: this is why the creation of Monsters and Decks has to follow some very important guidelines, let's see which ones.
The Hit Dices (HD) of the Monsters indicate their "power": this is the main stat for a monster, qualifying its strenght and danger level. AHQ3.0 provides dozens and dozens of standard or specific monsters, with their HD value: refer to these values when you are creating new monsters, comparing with existing ones and trying to use the same HD value related to the same stats combination. Generally speaking we can point the following generic HD values based on the different types of monsters:
1HD: animals, small thugs, weak humanoids
2/3HD: basic monsters as orcs, goblins etc. maximum 4W, stats never above 7, no special skill, generally never over 4DD.
4/5HD: strong members of the monster race: above 4DD sometimes, up to 5W, a couple stats on 8 and 9, DD that can reach 5DD and, rarely, 6DD.
6/8HD: very powerful members of the monster race: above 4DD, up to 6W, more than a couple stats on 8 and 9, special skills etc.
9+HD: strongest boss monsters, up to 8W and above (scale HD if the W go further, but the suggested maximum limit is always 9, except legendary monsters), special skills and much more make these monsters real war machines. Usually these are final monsters for hard and unique quests.
Being dozens and dozens of monster already included in the AHQ3.0 game, it's much more common for a game group the desire to create their own (maybe mixed with different races) decks. The creation of the decks is a very "delicate" process that doesnt have to break the balance of the game. Standard decks are built with the following scheme of Hit Dices (HD) combinations: the HD of an encounter is the sum of the monsters HD of that encounter, these schemes are called, using the original game terminology, Monsters Matrix:
6 cards of 1HD*
6 cards of 2HD
4 cards of 3HD
4 cards of 4HD
1 card of 6HD
* if there arent monsters available with 1HD for the monsters race involved, the 2HD is used.
As it's easily notices, the Wandering Monsters have encounters that cant be considered really deathly, and in general are less though than the Dens encounters. Only with a small possibility the Party can meet monsters cumulating more than 4HD, and the reasonable limit is fixed to 6HD (a single possibility over 17): the Decks composed with this classical structure is multiplied by two, creating a 34 cards deck, but all the combinations are possible and allowed till the indications on HD are respected. The Dens Cards Deck is composed by harder encounters, and its typical structure is the following:
4 cards of 2HD
4 cards of 4HD
6 cards of 5HD
4 cards of 6HD
2 cards of 7HD
2 cards of 8HD
2 cards of 10HD
2 cards of 14HD
The Dens allow encounters that can be very complex, of 6, 7, 8, 10 and 14 HD. Of course the informations indicated in the Monsters Matrix are generic and have to be understood as a guideline: there is no effective difference between a 9HD and 10HD encounter: the indicated scheme is a guideline for the creation of Decks, that is strongly suggested to follow to do not make the game unplayable or too hard/easy.