Cloudspire
How does the Espionage relic card work when you have no spire?
A single reply gives this, and no official ruling covers it.
- TKundNobody · Community · 2021-05-18
The card can be used at any time during the Onslaught Phase, since only words like immediately force timing. If you have no spire, the removed upgrades must be placed on an enemy spire, because every part of the card applies.