Underworld Knowledge opens up new dialogue options during certain conversations and quests. Additionally, it increases the amount of experience gained for each codex entry unlocked by 50%. This effect is not retroactive, but it will stack with other Knowledge perks as follows:
- One knowledge perk: 75XP per codex entry
- Two knowledge perks: 100XP per codex entry
- Three knowledge perks: 125XP per codex entry
- All four knowledge perks: 150XP per codex entry
- Champions of the Just - The Herald can use this perk to suggest getting in touch with their contacts in the lyrium smuggling market, as a way to supply the soon-to-be arriving templars. This will unlock the war table operation Secure More Lyrium for the Templars.
- In Hushed Whispers - The Herald can use this perk to suggest getting in touch with their contacts in the lyrium smuggling market, as a way to supply the soon-to-be arriving mages. Unlike Champions of the Just, this will not result in any war table operations.
- Strange Bedfellows - Can be used to recruit Ritts as an agent of the Inquisition, assigned to Leliana.
- Master of Horses - Can be used to recruit Horsemaster Dennet as an agent of the Inquisition. He will care for the Inquisition's horses himself.
- Business Arrangements - Can be used to recruit Sister Tanner as an agent of the Inquisition, assigned to Leliana.
- Sit in Judgment - When judging Crassius Servis, the perk can be used to recruit him as a smuggler for the Inquisition. This option unlocks the war table operation Judgment: Recover Sold Artifacts. However, this option does not add Servis as an agent; if you want to add him as an agent, choose to recruit him as an informant instead.
- Demands of the Qun - Adds an additional dialogue choice at the end of the quest for additional approval with Iron Bull. The option exists whether you saved the Chargers or not.
- Wicked Eyes and Wicked Hearts - Can be used during the dance with Grand Duchess Florianne de Chalons. When asked who you trust, the perk opens up several additional options. These include saying you trust no one, that you trust the Inquisition, or asking Florianne whom she trusts.
- Wicked Eyes and Wicked Hearts - The Ferelden mercenary encountered after evading the Venatori trap laid by the assassin can be persuaded to lend his troops to the Inquisition.