What is a secret on Devil's Playground?

Question

Team Liquid lists the following secrets for The Devil's Playground campaign mission:

Easter Eggs

Diablo

Can be found on an Island towards the southeast corner of the map.

I've found it, but can do nothing with him. What is a purpose of this secret? What can I do with those Diablo?

Answer 1

The fact that it exists at all is the secret. It's just a neat little reference to Diablo inside StarCraft, that's all. It doesn't do anything special other than look cool.

Answer 2

There is a mini Diablo in the bottom right (south-east) corner which is there just for decoration.

Here is a copy of a video which shows it. There really is nothing to do with it, its just there as a reference in between the different franchises in which Blizzard is known for doing.