The infestor is a cheap hero ontainable in early game or instantly if fast mode is choosen. the Infestor is a "stealthy" killer in the sense that its main ability Fungal Growth can be used from a safe distance and trap its effected targets in place and does massive damage basicly "one shooting" early marines and highly damaging mercs,
the infestor can burrow and move while burrowed but must unburrow to use fungal growth, so a little practice is needed to master its ambush style killing which can rack in some serious cash early game when sneaking into the front of your opponents base , useing fungal growth on all their bunched up marines and burrowing it.
the infestor is an easy to kill hero though and can be killed with ease if the player over extends it and gets scanned. also avoid the center beacon if its controlled by another player.
can morph into the Queen, giving it extra abilities such as spreading creep.