The Pariah Nexus box set for Kill Team introduced the Heavy Intercessors and the Flayed Ones figures to the game. If you're looking to pick these kits up without the other half, you will soon be able to as each is getting their own set for 40k.
From the article:
The recent release of Kill Team: Pariah Nexus saw the first appearance of the Space Marines’ brilliantly beefy Heavy Intercessors and freshly updated Necron Flayed Ones, and a lot of you have been eager to know when you can add more of them to your armies.
We have good news on that front – these units will be available in their own boxes in May.