Pocket Universe
From Archon Arcana - The KeyForge Wiki
Pocket Universe • Logos • Artifact • Rare • You may spend on Pocket Universe when forging keys.Action: Move 1 from your pool to Pocket Universe. • Artist: Atha Kanaani • Card Number: CotA:131, AoA:151, WC:172
Commentary
When an artifact with Æmber on it leaves play, the Æmber is returned to the common pool.
Source: Leaves Play
If there is enough Æmber on Pocket Universe (or other cards with this effect under the control of the active player) combined with the Æmber in the active player's Æmber pool during the "Forge a Key" step, the active player must forge a key.
Source: Forge