  Abell 2744, also known as Pandora's Cluster, is a complex merging galaxy
cluster. While a major merger is clear along the north-south axis, the
dynamical state of the northwest subcluster has been highly uncertain. We
present ultra-deep ($\approx$2.1 Ms) X-ray observations of Abell 2744 obtained
with the Chandra X-ray Observatory and reinterpret the multi-wavelength picture
with a suite of idealised simulations of galaxy cluster mergers. The new data
reveal in unprecedented detail the disruption of cool cores in the three X-ray
luminous subclusters and confirm the presence of a shock to the NW. A
position-velocity clustering of the cluster member galaxies shows a clearly
separated S2 component, with a $\Delta z$ implying a separation of 53 Mpc or a
line-of-sight velocity of $4500\ \rm{km \ s^{-1}}$, or likely some combination
of the two. While binary simulations allow NW to have undergone a gravitational
slingshot after the first pericenter passage, triple merger simulations rule
out this scenario, because the two mergers would have had to occur $\sim$0.5
Gyr apart, and the joint impact of the shocks from the two mergers would
completely disrupt the SE and NW cool cores; they only reform after 1-2 Gyr, by
which point the core separations greatly exceed observations. The scenario that
best describes Abell 2744 is a head-on N-S merger $0.5-0.6$ Gyrs ago followed
by a first infall of the NW subcluster. Furthermore, we note that a model with
three cluster-size halos, with masses consistent with gravitational lensing
constraints, nevertheless produces a lensing convergence and surface brightness
lower than observed in most of the field of view, whereas the temperatures are
consistent with observations. This suggests the presence of a large-scale
overdensity, which contributes to the diffuse emission and total surface
density without heating the densest gas.
