Where does Thaumaturgic Flux (Level 20) drop?

Thaumaturgic Flux (Level 20) starts dropping in areas of level 62 and above.

How many Thaumaturgic Flux (Level 20) stack in one slot?

Thaumaturgic Flux (Level 20) stacks up to 20 per inventory slot.

Expedition

Upgrades a Kalguuran Skill Gem to level 20

Right click this item then left click a Kalguuran Skill gem to apply it.

Except where noted: Removes a random modifier and augments a Rare item with a new guaranteed modifier

Thaumaturgic Flux (Level 20) can be made through Runesmithing — socket these runes into a Remnant of the matching size.

6 slots: Momentum Rune + Earth Rune + Ward Rune + Stone Rune + Arcane Rune + Oath Rune