this is a sketch of a protoss unit, looks like one that I saw on SC 2 but I have to say that I never thought in SC2 when I did this... pure coincidence.
The cross that is in the small circle in the middle of the unit means that there goes some sort of arm or phase disruptor cannon... or something. I dont' know about the measures of this thing but is tall enough to be used as a heavy artillery plataform (30, 40 or maybe 50 mts high). Useful in first assaults to wipe out enemy defenses while the rest of the army advences behind them.
They have an advenced AI system that allows them to take desitions and find the best way to deal or engage the enemy. They can be droped in the battlefield from any Carrier and start their attack at any moment.