The Battle of Hyrule Field

is the first HWAoC: in.

Overview
The Scenario starts off with King Rhoam sending the Hyrulean Army, which includes Link, to stop the army of Bokoblins, Moblins, and Lizalfos headed for Hyrule Castle.

There is one cutscene where Link finds a small, egg-shaped Guardian(Terrako), in a dormant state. Then, once Impa arrives from Purah with the Sheikah Slate in her hands, it activates the diminutive Guardian, which activates a Sheikah Tower. Once the cutscene is over, the diminutive Guardian seems to follow Link around.

Strategy
There is no particular strategy in this Scenario. The best thing to do would be to test out all the different buttons to see what they will do, as the next Scenario, Road to the Ancient Lab, is going to be much harder than this Scenario.