Seal of Vengeance

Seal of Vengeance is a Paladin seal obtained at 64, intended to replace Seal of Righteousness as the primary tanking seal. Initially it was only available to Alliance Paladins; post 3.0 Horde Paladins receive an equivalent at 66, Seal of Corruption.

Functionality
While activated, the Paladin's melee swings apply a debuff on the target that causes holy damage every 3 seconds for 15 seconds. The DoT stacks up to 5 times, with subsequent swings granting a damage bonus of direct holy damage and continuing to refresh the stack's duration. Furthermore, for every stack of Holy Vengeance on the target, Judgement's damage is increased by 10% (up to 50%).

Note that only normal melee swings can apply the debuff, with the exception of Hammer of the Righteous. Attacks like Divine Storm and Crusader Strike will not apply or refresh the DoT, though they do gain the direct holy damage bonus if the DoT has 5 stacks.

3.2 changes
In patch 3.2, the application of the debuff is treated as a melee attack. That is to say, it is not applied to the target automatically every time your melee swing lands—instead, when your melee swing lands, a separate melee attack is made to see if the debuff is successfully applied to the target. This separate attack can miss, be dodged, or be parried just like a regular melee special can.

Furthermore, in patch 3.2, if the target already has a 5-stack of Seal of Vengeance debuffs, each subsequent melee swing or special attack made while this seal is in effect will inflict 33% of the attacker's Weapon Damage as Holy damage to the target (twice this amount if the melee swing crits). This extra holy damage cannot miss, be dodged, or be parried.

Talents/Glyphs

 * Seals of the Pure - Increases the damage done by your Seal of Righteousness, Seal of Vengeance and Seal of Corruption and their Judgement effects by 3%/6%/9%/12%/15%.
 * Judgements of the Pure - Increases the damage done by your Seal and Judgement spells by 5%/10%/15%/20%/25%.
 * Glyph of Seal of Vengeance - Grants 10 expertise SKILL while Seal of Vengeance or Seal of Corruption is active.
 * Benediction (paladin talent) - Decreases the mana cost by 2%/4%/6%/8%/10%.

Tips & Tactics
This is a valuable seal for Tankadins, as the full 5 stack will do more holy damage (and therefore threat) per second than Seal of Righteousness. Additionally, Hammer of the Righteous can be used to maintain the DoT on up to three (four with the Glyph) targets at the same time.

It can also be useful in PvP against rogues who use Vanish, as the Damage Over Time component will force them out of stealth.

This seal is listed as magic, not melee so it can not miss, but it can, however, be resisted.

In PvP situations, it is not unknown for paladins who use this seal to carry a fast, 1 handed weapon (and normally a shield) to build up debuff stacks as fast as possible, then change to their slow, hard hitting 2h weapon after they reach 5 stacks to do burst damage.

Up to patch 3.2 this seal was used as a tanking seal.

This is very useful while tanking as it allows the paladin to switch targets while still maintaining aggro, and it allows the paladin to generate instant threat in the event of a threat wipe.

Since patch 3.2 it became the main DPS seal for Retribution Paladins against mobs with big amount of HP (bosses)

In PVP its usage is now limited - due to long time of stacking DOT.