As Gu Chengguang's secretary of many years, Zhang Tai could, to a degree, act as his representative. Opening the Dongli National Treasury required two Guardian Gods to be present, so Zhang Tai took Gu Chengguang's place.
As for why Gu Chengguang hadn't come himself, perhaps he was too busy, or perhaps it was to express his trust in Su Ze. 'See? I'm only sending a Butterfly Stage evolver with you into the treasury. I have no intention of monitoring you or showing distrust.'
Su Ze leaned toward the latter explanation.
The Dongli National Treasury was a completely sealed, airtight room constructed from Super Alloy.
A Butterfly Stage evolver and several soldiers stood guard in front of the main gate.
The soldiers saluted when they saw Su Ze and Zhang Tai approach, but they still had to verify both of their identities to prevent anyone from infiltrating in disguise.
Only after confirming their identities did they step aside to let the two men pass.
