Tumbaga Ingot is the weapon ascension material in Windrose. It is used at the Weaponsmith Workshop to ascend a Rare (blue) weapon to Epic (purple) rarity, unlocking that weapon's Epic-tier special effects.
Source
Tumbaga Ingots are found in chests tied to Blackbeard Treasure Maps. Each Blackbeard Treasure Map chest typically contains three ascension ingots. Treasure Maps drop from named encounters and boss-tier enemies in Blackbeard's fleet. The exact drop rate from specific enemies continues to be documented by the community.
Ascension Process
At the Weaponsmith Workshop's upgrade tab, a Rare weapon already leveled to 8 (via the Upgrade System) can be ascended to Epic by consuming Tumbaga Ingots. Ascension grants the weapon new Epic-tier passives on top of its existing stats. For example, a Rare Reliable Musket (+faster reload) becomes an Epic Reliable Musket (faster reload + 20% Critical Damage) after ascension. A Rare Sturdy Halberd becomes Epic with +15% Critical Hit Chance and +15 base damage.
Which Weapons to Ascend
Tumbaga is scarce, so plan ascensions carefully. Good ascension candidates are weapons that scale with your build's primary attribute, already show strong base stats, and have meaningful Rare or Epic effects. The Plague Halberd (Epic version restores 35% of max Health at 5 Corruption stacks) and the Rapier of a Thousand Cuts (bleed stacks with kill-transfer) are standout candidates for ascension.
See Also
Upgrade System - full weapon/armor upgrade path
Weapons - rarity tiers and effects
Blackbeard - treasure map encounters
Weaponsmith Workshop - ascension station