  This study presents observations of two possible substellar survivors of
post-main sequence engulfment, currently orbiting white dwarf stars. Infrared
and optical spectroscopy of GD 1400 reveal a 9.98 h orbital period, where the
benchmark brown dwarf has $M_2=68\pm8$ M$_{\rm Jup}$, $T_{\rm eff}\approx2100$
K, and a cooling age under 1 Gyr. A substellar mass in the lower range of
allowed values is favoured by the gravitational redshift of the primary.
Synthetic brown dwarf spectra are able to reproduce the observed CO bands, but
lines below the bandhead are notably overpredicted. The known infrared excess
towards PG 0010+281 is consistent with a substellar companion, yet no radial
velocity or photometric variability is found despite extensive searches. Three
independent stellar mass determinations all suggest enhanced mass loss
associated with binary evolution, where the youngest total age for an isolated
star is $7.5\pm2.5$ Gyr. A possible solution to this conundrum is the
cannibalization of one or more giant planets, which enhanced mass loss
post-main sequence, but were ultimately destroyed. PG 0010+281 is likely
orbited by a debris disk that is comfortably exterior to the Roche limit,
adding to the growing number of non-canonical disks orbiting white dwarfs. At
present, only L-type (brown) dwarfs are known to survive direct engulfment
during the post-main sequence, whereas T- and Y-type substellar companions
persist at wide separations. These demographics indicate that roughly 50
M$_{\rm Jup}$ is required to robustly avoid post-main sequence annihilation,
suggesting all closely-orbiting giant planets are consumed, which may
contribute to mass loss and magnetic field generation in white dwarfs and their
immediate progenitors.
