In my last thread, I mentioned abilities that one should NOT give to monsters. In this one I am listing things that I DO give to monsters.

All of these deal with armor class. In 1ed (and, I guess, 2ed), the monster information simply stated AC. In 3ed, the reasons for the AC are given, allowing for such things as a Touch AC. What I found playing 3ed was that those with WotC were really very unimaginative in assigning a monster AC. One will find with my monsters a number of factors being assigned to a monster's AC.

Deflection: This is assigned to indicate just how careful a person must be in approaching the creature. Monsters with spines, those with multiple legs, and others considerations of monsters have me give them Deflection to their AC. Deflection is considered protection against Touch attacks (as you still have to get close), but not against Range Touch. Deflection is never given a large amount. The normal value for Deflection is +2, but I have given monsters as much as +4.

Hardness: I never understood why WotC never used this. This was just another case where WotC had the topic in the rules, but never used it except in a limited way. Monsters with hard outer coverings are given Hardness. This is a subtraction to any physical damage done. This is not DR, as there is no way to get around this. While WotC simply makes monsters with tough armor to have a high Natural Armor (increasing the AC), it began simply giving high Natural Armor to high-level monsters simply to increase their AC -- thus destroying the logic of Natural Armor. Hardness allows me to create monsters with realistic armor classes, but end up being very hard to harm.

Absorption: Basically, the same as Hardness, except that the rational is completely different. In this case I have a monster with a very amorphous outer surface. Physical damage is subracted simply because not all the damage will be transmitted to the creature. My Aboleth has Absorption listed in its AC, as its slime coating helps to protect the creature from harm. Again, this is not DR, as there is no way to get around it. Note however that monsters with Absorption usually have DR or Resistances as well, as things like a liquid outer covering will protect them from fire, etc.

Note that in the latter cases, this adds a letter to the Armor Class. For example, the armor class for my Aboleth --

AC: 16A (-2 Size, -1 Dex, +4 Deflection, +5 Natural & 4 Absorption)

Note that my Aboleth really does not have a high Armor Class, but it still presented itself as a very tough opponent to those attempting to get close to it. Also, by giving it Deflection (instead of just +9 Natural Armor) I am stating that this creature has sharp fins, whiskers, and that slimey skin that just make getting close to it difficult. This aids in role-play in informing the players about the challenge of fighting this monster.

While on the topic, let me also present the Armor Class of my Large Trapdoor Spider --

AC: 15C (-1 Size, -1 Dex, +2 Deflection, +5 Nat. & Cover)

Note that again the monster did not have a high Armor Class. Deflection in this case is given because of the multiple legs, the hairs on the legs, and the usual strands of webbing the monster lays down to enable it to detect things around its lair (which also gives the monster a limited Tremorsense). I however note that Cover should apply to the Armor Class, as this monster seldom comes fully out of its lair (the cover bonus changed round to round depending on how far out the monster came). Further note: I also put a 'C' behind the AC to inform me of Concealment should the monster be naturally difficult to detect or contact.

Hopefully, these notes will allow others to create monsters with a little more variety.

The way you describe the deflection ac, it would be more accurate to have it be a circumstance bonus to ac.