  With two central galaxies engaged in a major merger and a remarkable chain of
19 young stellar superclusters wound around them in projection, the galaxy
cluster SDSS J1531+3414 ($z=0.335$) offers an excellent laboratory to study the
interplay between mergers, AGN feedback, and star formation. New Chandra X-ray
imaging reveals rapidly cooling hot ($T\sim 10^6$ K) intracluster gas, with two
"wings" forming a concave density discontinuity near the edge of the cool core.
LOFAR $144$ MHz observations uncover diffuse radio emission strikingly aligned
with the "wings," suggesting that the "wings" are actually the opening to a
giant X-ray supercavity. The steep radio emission is likely an ancient relic of
one of the most energetic AGN outbursts observed, with $4pV > 10^{61}$ erg. To
the north of the supercavity, GMOS detects warm ($T\sim 10^4$ K) ionized gas
that enshrouds the stellar superclusters but is redshifted up to $+ 800$ km
s$^{-1}$ with respect to the southern central galaxy. ALMA detects a similarly
redshifted $\sim 10^{10}$ M$_\odot$ reservoir of cold ($T\sim 10^2$ K)
molecular gas, but it is offset from the young stars by $\sim 1{-}3$ kpc. We
propose that the multiphase gas originated from low-entropy gas entrained by
the X-ray supercavity, attribute the offset between the young stars and the
molecular gas to turbulent intracluster gas motions, and suggest that tidal
interactions stimulated the "beads on a string" star formation morphology.
