Your command center is your base. It continually spawns marines, and contains most of the basic upgrades (the rest in marine shop, merc shop, and unit shop) and provides all of the defense towers. It also builds all mercenary compounds, spawns heroes, and can utilize a scanner sweep. If you lose this, you lose most of your upgrades, marine spawning, and destroys your merc compound. If it is not faster or fastest, you can use your infested saviors 3 times. More can be bought in the marine shop.