With Patch 3.0, prior to the release of Wrath of the Lich King, Blizzard introduced Inscription into the game. Glyphs that are crafted via inscription modify spells and abilities by increasing their damage or removing reagent requirements. Sometimes they completely change the way a spell works. Every level 80 character has 6 slots for glyphs, 3 major and 3 minor. Major glyphs provide a damage boost or a significant change to a spell while minor glyphs do minor things, often of cosmetic nature. Glyphs are created by a scribe who needs parchment, which is bought from vendors, and ink for their creation. Ink can be obtained by milling herbs. What type of ink one creates depends on the level of the herbs. Most glyphs used in high end content require Northrend herbs.

The glyph choice depends on the Warlock's talent spec. Every Warlock wants to strengther their usual companion, so they chose the Glyphe of the Imp, Fel Guard or Fel Hound for Destruction, Demonology and Affliction respectively. The next glyph slots is used for boosting the main "nuke" like Shadowbolt or Incinerate. The final major glyph is a matter or taste. Glyph of Corruption is similar to the Nightfall talent and gives instant Shadowbolts. Other glyphs are able to increase the duration of Curse of Agony or increase Life Drain's effect.

The minor Glyph of Drain Soul is the first choice for minor glyphs, as it allows the Warlock to gain an additional Soul Shard from an enemy. Glyph of Unending Breath increases the swimming speed of the buffed target - while not game changing this is surely nice to have.