Not only the super-Venus in terms of an ultra hot thick atmosphere, but at 13 Me, it would hold onto heat a LOT longer than Earth or Venus. Even at 4 billion years old I'd imagine it would have an incredibly high rate of volcanism, and hate to image what it must have been like when a billion years old. Not to mention if there is additional heat input from tidal friction. Heck, maybe the whole thing is a big ball of magma.

Assuming it is tidally locked, I wonder what the amospheric circulation would look like? I would think you would get some incredible winds. And with a thick, hot atmosphere, probably full of corrosive volcanic gasses -- or even just supercritical CO2, H2O, or whatever is likely -- with very fast winds, weathering would be something fierce!

A thick atmosphere would tend to equalize temperatures, but if it had no atmosphere, just one fact at 1000K and one facing cold dark space, what would that do to mantle circulation?

Sounds like a fascinating planet, if not exactly where an interstellar Club Med is likely to be built...