1.10 -- Cloak of Shadows (CoS)

Properties of CoS:

1) Unlike in 1.09, damage does not dispel the 'blindness' effect of CoS. The enemy vision radius of the monster while blinded is 1, but if a monster to be doing something(eg. chasing you) when you cast CoS, he will continue to do so(until you interrupt him, with a Psychic Hammer, for example), then remain stationary when the action is finished.
2) CoS dispels Firewalls(in the Arcane Sanctuary).
3) CoS prevents Shamans from reviving Fallen, Flesh Spawners from creating babies, Sand Maggots from laying eggs and ranged attackers from firing.
4) CoS forces monsters to use their melee attack, even if they are in range for a secondary attack(eg. Balrogs will never use their Inferno ability when CoS is active).
5) CoS does not work on Bosses, Champions, Superuniques, Minions of Destruction, and Oblivion Knights.
6) CoS's defense bonus is treated differently from any other defense modifier(except RibCracker's defense bonus, which is additive with CoS's bonus). Hence, it is multiplicative, not additive, with other defensive modifiers, such as Defiance and Shout. To understand how this works, a bit of explanation on how to calculate a character's defense is needed:

A): Find the base defense of a character. For player characters, this is just Dexterity/4 and rounded down. For hirelings this should be their Dexterity/4 rounded down, plus whatever defense they gain from levels.

B): Find the item defense of a character. This is the sum of all defense you obtain from items, which includes your helm, armor, shield, gloves, belts, and boots. Note that +%defense on items that have a defense number are exclusive to that item alone. So, if you have a Helmet with a base defense of 5(and a +100% defense mod on it, making the total helmet defense 10) and a Quilted Armor with a base defense of 10(and a +50% defense mod on it, making the total armor defense 15), you would have an item defense of (10 + 15) = 25, not (5 + 10) * 2.5 = 37.5

C): Multiply item_armor_percent bonuses to the results of #B, then round down(the bonuses below are additive with each other):
Sources of item_armor_percent include
- Valkyrie defense bonus
- Spirit Wolf defense bonus
- Dire Wolf defense synergy from Spirit Wolf
- Grizzly defense synergy from Spirit Wolf
- Cloak of Shadows defense bonus
- +%Defense on items without a defense number(eg. rings, amulets, weapons. So, instead of +%Defense usually being applied only on the item it's on, +%Defense on weapons/rings/amulets are effectively being applied on every single piece of equipment. It's this property that makes RibCracker such a popular weapon on characters focusing on defense).

D): Sum up the results of #A and #C to obtain total character defense.

E): Multiply skill_armor_percent bonuses to #D, then round down to find total defense(eg. what's being used for calculating the chance a monster hitting you. Again, the bonuses below are additive with each other):
Sources of skill_armor_percent mods include:
- All Sorceress cold armors
- Paladin's Defiance, Conviction, Holy Shield
- Barbarian's Shout, Concentration, Iron Skin, Battle Cry
- Werebear defense bonus
- Cloak of Shadows debuff
- Shadow Warrior defense bonus
- Overseers whipping their minions
- Succubi defense curse

The result is that CoS multiplies the item defense, before other +%Defense modifiers on skills are put into effect. In the end, you get a much higher defense than you would usually have, had CoS's +%Defense bonus been a skill_armor_percent bonus instead of a item_armor_percent(especially if you have a lot of bonuses from the skill_armor_percent section). Whether this property is a bug(since it's the only skill in the item_armor_percent section that affects the character and not the minion) or a feature remains to be seen.

Thanks to Zath and Frenzied Bovine.