Abstract

Significant international investment over the last decade has resulted in new cluster surveys that can deliver precise measurements of key cosmological parameters. However, are those measurements accurate? Recent results from clusters detected by the Dark Energy Survey (DES) are in significant tension with those from other cosmological probes. This tension is most likely due to hitherto uncorrected systematic effects in the analysis. So is it Game On or Game Over for cluster cosmology? In this talk I will review the latest DES cluster cosmology results and the recent work by the XMM Cluster Survey in support of that work. I will also describe our re-analysis of eROSITA data from the eFEDS data release, an exploration of anisotropy in X-ray scaling relations, and new results regarding the purported 3.5keV dark matter line. I will end with an overview of our plans to extend our X-ray Cosmology work with future data releases from LSST and eROSITA.