  Both the origin of, and the population demographics of, massive black holes
(MBHs) remains an open question in modern day astrophysics. Here we introduce
the BlackDemon suite of cosmological simulations using the Enzo code. The suite
consists primarily of three, high resolution, distinct regions, each with a
side length of 1 h$^{-1}$ Mpc. Two of the regions evolve within a larger
overdense region while the other evolves within a more `normal' region. The
simulation suite has spatial and mass resolution capable of resolving the
formation of the first galaxies and MBHs within each region. We report here, as
the first in a series of papers, the evolution of the simulation suite up to
the point where star formation has commenced in each region and for 2 Myr after
the onset of star formation. Within these environments the masses of the first
objects to form have masses between approximately 100 M$_{\odot}$ and $10^4$
M$_{\odot}$. The larger mass objects form due to both major mergers, which
trigger rapid mass inflow to the centre of the halo, and also through multiple
minor mergers which allows the host halo to grow to close to the atomic cooling
threshold. In both scenarios the initially very high accretion rates quickly
grow the objects to close to $10^4$ M$_{\odot}$. However, accretion halts after
less than 50,000 years due to gas starvation. The final fate of these objects
in terms of fragmentation and subsequent fragment mergers cannot be deduced at
our current resolution. In the case where fragmentation is mild such objects
are likely to form super-massive stars before contracting to the main sequence
evolving into massive population III stars and subsequently MBHs.
