  We obtain finite-temperature M2 black branes in 11-dimensional supergravity,
in a $G_4$-flux background whose self-dual part approaches a solution of
Cveti\v{c}, Gibbons, L\"u, and Pope, based upon Stenzel's family of Ricci-flat
K\"ahler deformed cones. Our solutions are asymptotically $AdS_4$ times a
7-dimensional Stiefel manifold $V_{5,2}$, and the branes are ``smeared'' to
retain $SO(5)$ symmetry in the internal space. The solutions represent a mass
deformation of the corresponding dual $CFT_3$, whose full description is at
this time only partially-understood. We investigate the possibility of a
confinement/de-confinement phase transition analogous to the $AdS_5 \times S^5$
case, and a possible Gregory-Laflamme type instability which could lead to
polarised brane solutions which break $SO(5)$. We discuss possible consequences
for AdS/CFT and the KKLT cosmological uplift mechanism.
