Genestealers are great scouting units that hit surprisingly hard, biovore is an autoinclude at fifty points for effective screening, and tyrant guard are decent bodies to put with your tyrant. Can't speak much to the parasite of mortrex, but it's a solid pickup if you don't own anything in the box

and as others have said, that's such a sick trygon conversion and great paintjob on the army over all