Sneak attack

Sneak Attack

Usage: Passive
Prerequisite: none

Description

Rogues (or any other character with a source of sneak attack damage) may do additional damage when attacking an opponent if one of the following conditions is met:

The target is unaware of the character's presence.
The target is attacking another player (possibly under the influence of Intimidate from that player or Diplomacy from the passive character).
The target is under the effects of a successful Bluff.
The target is helpless.
The target is blind.
The target is under the effects of a Deception item or attack.

Targets immune to critical hits (such as an undead, slime, construct, elemental, or anything with a Fortification of 100% or higher) are also immune to Sneak Attack bonus damage. Effects that decrease or bypass fortification can partially break this immunity - if you can bring a creature's effective Fortification (their natural Fortification - all effects decreasing their Fortification - your Fortification bypass) below 100%, Sneak Attack has the same chance to work as a normal critical hit, and will always work if their effective fortification is reduced to 0%. However, some rare creatures appear to be completely immune to sneak attacks, and won't receive them even if a large portion of their fortification is being bypassed - only certain abilities in Sneak Attack-related trees, like Assassin's Trick, Wracking Shot, and Shadowdancer's capstone, can bypass this immunity.

Ranged sneak attack

Ranged and missile weapons normally deal Sneak Attack damage only if the target is within 15 meters (49 ft).
Deepwood Stalker enhancements, Mechanic enhancements, Elf enhancements and various elven subraces can increase this range.

(Note that the /loc chat command shows your current location in meters.)

Sources of sneak attack damage

Class feats

Rogue

Enhancements

All rogue trees: Assassin enhancements, Mechanic enhancements, Thief-Acrobat enhancements
Monk Ninja Spy enhancements
Ranger Deepwood Stalker enhancements
Druid Nature's Warrior enhancements
Wizard Pale Master enhancements
Halfling enhancements
Shadar-kai enhancements

Items

Epic / past life bonuses

Past Life: Rogue
Past Life: Dark Hunter
Scion of the Ethereal Plane
Shadowdancer cores
Fatesinger Martial Hymn (since Update 43)

Enhancements that enable sneak attack

Ninja Spies can also train Unbalancing Strike, which causes a Bluff effect that makes enemies briefly vulnerable to Sneak Attacks in direct combat.
Shiv
Called Shot
Harper Enchantment of Deception
Gloom Stalker

Sneak attack damage

The Sneak Attack damage cannot critically hit.
Since Update 25 Patch 2 Sneak Attack Damage now scales with 150% Melee or Ranged Power.
An extra sneak attack dice/die is a +1d6 sneak attack damage (average of 3.5 damage)
Sneak attack damage scales with Vulnerability, additional damage against helpless monsters, and similar effects that increase damage. However, it is not displayed correctly; additional damage is added to the first number. DDO Vault

Notes

Item descriptions and tooltips related to Sneak Attack can sometimes be misleading.

For example a Legendary Animated Rope displays the following: "Sneak Attack Bonus +14: Provides a +14 to attack bonus and a +22 to damage for any attack that would qualify as a Sneak Attack, even if the wielder is not a Rogue."
The actual in-game effect is: "+14 to attack bonus when sneak attacking and +22 to Sneak Attack Damage when sneak attacking."
The above example applies to everything that is beneficial to your Sneak Attacks (items, feats, enhancements). Your base damage remains unaffected. Only your Sneak Attack Damage is increased.

Gameplay implications

Allowing Sneak Attacks to work on targets attacking another player is an important change to DDO from the PnP rules. As long as someone else has "aggro", the Rogue gets a damage bonus of 1d6 per two levels. Even at level 1, that's an average of 3.5 more damage per hit. And you will get that bonus damage for at least two or three hits, typically, since it takes that long for a monster to turn aggro from another player onto you.

Although the +2 flanking bonus to melee attack rolls is especially useful to Rogues, who have a lower Base Attack Bonus than the warrior classes, attacking an enemy from behind is not required to score Sneak Attack damage.

Attacking while Sneaking isn't required either! In fact, it's counterproductive to take more than a swing or two in Sneak mode since your attack rate is so much slower than normal. Use it to help make sure someone else gets aggro first, then turn it off when you start swinging. Or simply let other members of your party charge ahead and don't join them until they're engaged.

The "helpless" condition is important to remember. Many spellcasters (including Wizards, Sorcerers, Clerics, and even Bards) can render enemies helpless through direct spell effects like Hold Person, or indirectly through ability damage. Some weapons' special effects can cause the "helpless" condition as well, such as Stonedust Handwraps or Shield of Reflecting (but not paralyzing weapons). This can lead to an unfettered flurry of Sneak Attack damage on that victim and defeat him in short order. One dark Monk finishing move, Freezing the Lifeblood, is a paralysis attack that also makes victims helpless.

The "blindness" condition is also significant to sneak attack. A blind monster receives sneak attack damage even if the player character has aggro. Blindness can come from spells such as Blind, or Sunburst, the dark finishing move Falling Star Strike, and is a special effect from a Green Steel Radiance II weapon and Radiance II Guard items, or the specific Dragontouched Armor's Sovereign Tier III rune. Radiance and Radiance Guard are also available as a suffix on high level loot-generated items.

A successful use of Bluff will make an enemy vulnerable to sneak attacks for six seconds, even if you're its target. Improved Feint allows you a second (and area effect) method of bluffing. Half-Elves have an additional racial bluff, and Monks can train Unbalancing Strike, an elemental ki attack which causes a bluff effect, from any of their class trees.