Titan Residuum

Titan Residuum is a Battle for Azeroth currency. It is used to purchase Azerite armor.

Source
There are four sources for this currency:


 * Weekly Mythic+ chest
 * Scrapping Azerite armor by using a scrapper
 * Disenchanting Azerite armor
 * As a reward from certain Treasure Map missions.

Mythic+
The weekly Mythic+ chest is a primary source of Titan Residuum. The amount contained is based on the highest Mythic+ keystone level successfully completed, with higher-level keys awarding exponentially higher amounts. These gains continue to increase past Mythic+ Level 10 at a fixed amount. The amounts of Titan Residuum awarded by the chest are increased with each Mythic+ season.

Scrapping/Disenchanting
Titan Residuum can also be obtained by breaking down Azerite armor via scrapping or disenchanting. Each item scrapped or disenchanted will always award a fixed amount of Titan Residuum based on its item level (unaffected by Azerite Empowered).

 400 and 415 item levels obtained after patch 8.2.0 had previously yielded higher Titan Residuum when scrapped.

In order for Azerite armor items to yield Titan Residuum, the following requirements must be met:
 * The item must have been obtained during or after patch 8.3.0.
 * The item must be of both quality and item level 430.
 * A quality item will never yield Titan Residuum regardless of its item level.
 * quality items below item level 430 no longer yield any Titan Residuum.
 * The item's armor type must match the armor type intended for the character's class (a hunter can only gain Titan Residuum from mail Azerite armor).
 * Crafted Azerite pieces (Engineering Goggles) will never yield Titan Residuum.

Mission Table
Titan Residuum is a potential reward from Mysterious Treasure missions. These missions are granted by the Mysterious Treasure Map, a reward from completing the weekly Island Expedition Azerite quests: Only one map per week can be gained per character. Unlike the other three sources, Titan Residuum only has a chance of being the mission reward and is not guaranteed.
 * Azerite for the Alliance
 * Azerite for the Horde

For Season 4, the amount awarded by these missions varies between.

As a currency
Titan Residuum is used to purchase Azerite armor from Thaumaturge Vashreen. It can purchase either a Relinquished Azerite Token (each slot has its own token), which contains a class-appropriate Azerite armor piece equivalent to the token's item level, or to purchase specific pieces of Azerite gear.

Titan Residuum is also used to purchase Rank 4 Mythic+ Azerite essences. Each essence costs for Season 4 ( during Season 3).