  Inner Oort Cloud objects (IOCs) are Trans-Plutonian for their entire orbits.
They are beyond the strong gravitational influences of the known planets yet
close enough to the Sun that outside forces are minimal. Here we report the
discovery of the third known IOC after Sedna and 2012 VP113, called 2015 TG387.
2015 TG387 has a perihelion of $65 \pm 1$ au and semi-major axis of $1170 \pm
70$ au. The longitude of perihelion angle, $\bar{\omega}$, for 2015 TG387 is
between that of Sedna and 2012 VP113, and thus similar to the main group of
clustered extreme trans-Neptunian objects (ETNOs), which may be shepherded into
similar orbital angles by an unknown massive distant planet, called Planet X or
Planet Nine. 2015 TG387's orbit is stable over the age of the solar system from
the known planets and Galactic tide. When including outside stellar encounters
over 4 Gyrs, 2015 TG387's orbit is usually stable, but its dynamical evolution
depends on the stellar encounter scenarios used. Surprisingly, when including a
massive Planet X beyond a few hundred au on an eccentric orbit that is
anti-aligned in longitude of perihelion with most of the known ETNOs, we find
2015 TG387 is typically stable for Planet X orbits that render the other ETNOs
stable as well. Notably, 2015 TG387's argument of perihelion is constrained and
its longitude of perihelion librates about 180 degs from Planet X's longitude
of perihelion, keeping 2015 TG387 anti-aligned with Planet X over the age of
the solar system. We find a power law slope near 3 for the semi-major axis
distribution of IOCs, meaning there are many more high than low semi-major axis
IOCs. There are about 2 million IOCs larger than 40 km, giving a mass of
$10^{22}$ kg. The IOCs inclination distribution is similar to the scattered
disk, with an average inclination of 19 degs.
