The Jarrasul is the Vasari's colonization capital. Colonization bonus is reduced structure build times (20%) for 240/480/720 seconds.
It's well known for its Nano-Disassembler ability, which does 30 dmg per second (I believe for 20/30/40 seconds) and an armor reduction of -2/-4/-6.
At level 6, this capital becomes a seige engine with Drain Planet, earning 15.0 resources per second and doing 45.0 planet bombing damage per second for 30 seconds (overall damage 1350). This ability is interruptable, so don't give it orders while performing Drain Planet unless you have to.
Its other ability is Gravity Warhead, which disables ships from phase jumping and reduces maximum speed by 30%/45%/60% and acceleration by 60%/80%/120% for 12/15/18 seconds.