Sigil of Power

The subject of this article could only be obtained prior to patch 6.0.2.

Source

This item drops from all raid boss encounters as personal loot in Mogu'shan Vaults, Heart of Fear, Terrace of the Endless Spring, Throne of Thunder or the eight first bosses in Siege of Orgrimmar. The sigils will drop in all four raid modes: Raid Finder, Flexible (for Siege of Orgrimmar), 10/25-player Normal, and 10/25-player Heroic. The chance for the item to drop is one attempt per eligible boss, per week across all difficulties, and the chance for the item to drop is the same regardless of difficulty mode. Lei Shen and the Sha of Pride have a 100% drop rate.

Patch 6.0.2 (2014-10-14): Removed.
Patch 5.4.0 (2013-09-10): All bosses in Throne of Thunder now have a chance to drop either a Sigil of Power or Sigil of Wisdom. The first eight bosses in Siege of Orgrimmar have a chance to drop a Sigil of Power, Sigil of Wisdom, Secrets of the Empire, or Titan Runestone.
Patch 5.3.0 (2013-05-21): The Strength of One's Foes: All bosses in Mogu'shan Vaults, Heart of Fear, and Terrace of the Endless Spring now have a chance to drop either a Sigil of Power or Sigil of Wisdom.
Hotfix (2013-01-22): "Sigils of Power now only drop in Mogu'shan Vaults, and Sigils of Wisdom will only drop in Heart of Fear and Terrace of Endless Spring, with a very small chance to drop in LFR Mogu'shan Vaults. This should ensure that players who had access to Mogu'shan Vaults for a longer period of time are now seeing more Sigils of Wisdom."
Patch 5.0.4 (2012-08-28): Added.

Permanent equipment

	[Sulfuras, Hand of Ragnaros] [Thunderfury, Blessed Blade of the Windseeker]

	The Twin Blades of Azzinoth [Warglaive of Azzinoth] (main hand) [Warglaive of Azzinoth] (off-hand) [Thori'dal, the Stars' Fury]

	[Val'anyr, Hammer of Ancient Kings] [Shadowmourne]

	[Dragonwrath, Tarecgosa's Rest] Fangs of the Father [Golad, Twilight of Aspects] (main hand) [Tiriosh, Nightmare of Ages] (off-hand)

	See Legendary Legion equipment

	[Ashjra'kamas, Shroud of Resolve]

Encounter-limited weapons

	[Cosmic Infuser] [Devastation] [Infinity Blade] [Netherstrand Longbow] [Phaseshift Bulwark] [Staff of Disintegration] [Warp Slicer]

Items

	[Eye of Sulfuras] [Enchanted Elementium Bar]

	[Crystallized Dread] [Crystallized Horror] [Crystallized Terror] [Capacitive Primal Diamond] [Courageous Primal Diamond] [Indomitable Primal Diamond] [Sinister Primal Diamond]

	[Book of Flight Form]

	[Corrupting Core] [Horrific Core] [Voidborn Core] [Malefic Core]

Quest items

	[Bindings of the Windseeker] (left) [Bindings of the Windseeker] (right) [Vessel of Rebirth] [Dormant Wind Kissed Blade]

	[Fragment of Val'anyr] [Shattered Fragments of Val'anyr] [Unbound Fragments of Val'anyr] [Reforged Hammer of Ancient Kings] [Shadowfrost Shard]

	[Heart of Flame] [Seething Cinder] [Shadowy Gem] [Elementium Gem Cluster] [Fragment of Deathwing's Jaw]

	[Core of Flame] [Core of Iron] [Core of Life] [Corrupted Blood of Teron'gor] [Abrogator Stone] [Abrogator Stone Cluster] [Felbreaker's Tome] [Sigil of the Sorcerer King] [Elemental Rune] [Elemental Tablet] [Heart of the Fury] [Draenic Thaumaturgical Orb] [Flamebender's Tome] [Blackhand's Severed Arm] [Orb of Dominion] [Tome of Chaos] [Draenic Sea Chart]

	[Damaged Thunderfury] [Thunderfury, Blessed Blade of the Windseeker] [Emberscar, Brand of Damnation]

	[The Curse of Stone] [Torn Page of "The Curse of Stone"] [The Final Truth] [Torn Page of "The Final Truth"] [Fear and Flesh] [Torn Page of "Fear and Flesh"]

Removed from game

Permanent weapons	Atiesh [Atiesh, Greatstaff of the Guardian] (druid) [Atiesh, Greatstaff of the Guardian] (mage) [Atiesh, Greatstaff of the Guardian] (priest) [Atiesh, Greatstaff of the Guardian] (warlock)

Encounter-limited weapons	[Andonisus, Reaper of Souls] [Bundle of Nether Spikes] ([Nether Spike])

Items	[Black Qiraji Resonating Crystal] [Talisman of Binding Shard] [Eye of the Black Prince] Shroud of the Celestials [Fen-Yu, Fury of Xuen] [Gong-Lu, Strength of Xuen] [Jina-Kang, Kindness of Chi-Ji] [Qian-Le, Courage of Niuzao] [Qian-Ying, Fortitude of Niuzao] [Xing-Ho, Breath of Yu'lon] [Sanctus, Sigil of the Unbroken] [Thorasus, the Stone Heart of Draenor] [Etheralus, the Eternal Reward] [Maalus, the Blood Drinker] [Nithramus, the All-Seer] [Crystallized Fel]

Quest items	[Frame of Atiesh] [Splinter of Atiesh] [Mysterious Note] [Sigil of Power] [Sigil of Wisdom] [Chimera of Fear] [Secrets of the Empire] [Lightning Lance] [Tempered Lightning Lance] [Titan Runestone] [Heart of the Thunder King]

Not available to players

[Ashbringer] [Breath of the Black Prince] [Crafty's Pole] [Crown of Heaven] [Enchanting Test Sword] [Foror's Fabled Steed] [Fudgehammer] [Pearl of Farahlon] [Peep's Whistle] [Shard of the Defiler] [Soaked Ogre Decoder] [[PLACEHOLDER TIER 3 ITEM]]