Kemocite is a key ingredient used in the Xindi weapon. It was also the substance in the hold of Quark's ship in Little Green Men (1995) that caused the ship to travel back in time to the 1950's.
As of this episode, Enterprise has been in the Expanse for three months.
Gralik Durr reveals how the Xindi homeworld was destroyed. Enterprise saw the remains in The Xindi (2003).
This episode contains the first mentioning of the sixth Xindi sub-species, the Avians. There were plans to also have representatives of the Avians on the Xindi Council, but there were issues in depicting them on-screen. Creating them with computer-generated special effects would have been too costly since there were already two species that had to be animated that way (the Aquatics and the Insectoids); dressing actors up as "bird people" was felt to look ridiculous. In the end, the Avians were explained as simply having gone extinct.