This was a world of fantasy, and there were real deities, so naturally, the statues of the gods were not ordinary sculptures.
However, the methods by which the statues could possess spiritual energy and function were quite limited. The first was to obtain divinity, a process by which a deity's spiritual power descended, using the statue as a medium.
The second method was that devotees' long-time worship and offering could also grant some of the deity's power.
And the most supreme method was to first be bestowed with divinity and then to receive the worship of believers. In fact, all gods with faithful followers did so.
The guild also had various statues, and using offerings to sacrifice for temporary power was another way the statues could be used.
Put simply, it was a transaction with the gods, sacrificing offerings to obtain certain powers, with each side getting what they needed without owing each other anything.