FAQ - Age of Empires 2 Definitive Edition
What Do Relics Do in Age of Empires 2 ?
A. Relics give gold. 1 relic trickle 1 gold per ~2 seconds. The more relics you have the more gold start trickling. Aztecs civilization has a team bonus that lets you and your allies generate more gold from relics.
Here is a short video showing the gold trickling effect of relics:
