We discuss the importance of Fe23+ in determining the line intensities of Fe XXV Kα complex in an optically thick cloud, and study the prediction of Liedahl (2005) on Resonance Auger Destruction (RAD) with Cloudy in the context of Perseus cluster. A Fe XXV Kα line photon can change/lose its identity upon absorption by three-electron iron as a result of “line interlocking”. This may lead to autoionization of the absorbing ion, ultimately destroying the Fe XXV Kα photon by RAD. Out of the four members in Fe XXV Kα complex, a significant fraction of the x line photons get absorbed by Fe23+ and destroyed, causing the x line intensity to decrease. For example, at a hydrogen column density of 1025 cm-2, ~30% of the x photons are destroyed due to RAD. w and z are unaffected, while the line intensity of y is slightly (≤10%) reduced.