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We present active galactic nuclei (AGNs) that have shown extreme amplitude variability in X-rays. These AGN appear as bright for long periods, but then suddenly become extremely X-ray weak sources. Most likely this behavior is due to strong absorption along the line of sight or by relativistically blurred reflection. Two extreme examples are the Narrow Line Seyfert 1 (NLS1) galaxies WPVS 007 and Mkn 335. WPVS 007 is a peculiar AGN because it combines the properties of a normal NLS1 with those of a broad-absorption line (BAL) quasar, which typically only appear in high-luminousity, high black hole mass systems. Mkn 335 has appeared an an X-ray bright AGN for most of the past few decades, but was caught by Swift in a deep X-ray flux minimum state in 2007, and has remained in that state for most of the time since. One potential explanation for this low state is absorption. Several Other AGN have been in deep minimum X-ray flux states, including PG 0844+349 and 1H 0707–495, for which the dramatic drops in X-ray flux have been explained by blurred X-ray reflection.

PHL 1092 is a z ∼ 0.4 high-luminosity counterpart of the class of Narrow–Line Seyfert 1 galaxies. In 2008, PHL 1092 was found to be in a remarkably low X-ray flux state during an XMM–Newton observation. Its 2 keV flux density had dropped by a factor of ∼ 260 with respect to a previous observation performed 4.5 yr earlier. The UV flux remained almost constant, resulting in a significant steepening of the optical-to-X-ray slope αox from − 1.57 to − 2.51, making PHL 1092 one of the most extreme X-ray weak quasars with no observed broad absorption lines (BALs) in the UV. We have monitored the source since 2008 with three further XMM–Newton observations, producing a simultaneous UV and X-ray database spanning almost 10 yr in total in the activity of the source. We present here results from our monitoring campaign.