  Interplanetary Coronal Mass Ejections (ICMEs) are prominent drivers of space
weather disturbances and mainly lead to intense or extreme geomagnetic storms.
The reported studies suggested that the planar ICME sheath and planar magnetic
clouds (MCs) cause extreme storms. Here, we investigated the severe two-step
geomagnetic storm ($Dst \sim -187$ nT) of 25$^{th}$ solar cycle. Our analysis
demonstrates flattened (pancaked) ICME structures, i.e., quasi-planar magnetic
structures (PMS). The study corroborates our earlier reported finding that the
less adiabatic expansion in quasi-PMS transformed ICME enhanced the strength of
the southward magnetic field component. It contributes to the efficient
transfer of plasma and energy in the Earth's magnetosphere to cause the
observed severe storm.
