It's just a picture of a footman with a command aura, apparently anytime a building is constructed, a unit is created, a unit dies, Anywhere in the map, ANY unit/s affected by the auras-- "trueshot aura/command aura" will flicker the bonus damage and in some cases when you attack it doesn't register during the moment it flickers which is a big deal if your units have critical hits and fast attack speed in which some cases the damage crits normally for 100k and sometimes 50k despite having no changes in stats just because the command aura updated.