Phyla-Vell's yellow passive 'If Moondragon is on the team, if match damage would reduce either Moondragon or Phyla-Vell to less than 8% health (including downed) they are instead healed to 8% health' is triggering even without Moondragon being present, making Phyla-Vell immune to death by match damage.
https://www.youtube.com/watch?v=XMlfrbQb-Ow
Hi Jezequel! Thanks for this report.
We have confirmed a fix for this issue that will go live with the next data patch. Thanks again!