Where is Cao Cao?

I've played this game for 2 months now, not a single time had I see a Cao Cao in a match, or any where. He is not in the prize of freebies, he is not shown in HOK camp website, and he has 0.01% pick rate.

What's the deal with this seemingly normal hero having such an abnormally low pick rate and an almost non-existed presence?

For reference, the least picked hero according to HOK camp are Athena and Agudo, at 0.14% and 0.19%