  Strong band engineering in two-dimensional (2D) materials can be achieved by
introducing moir\'e superlattices, leading to the emergence of various novel
quantum phases with promising potential for future applications. Presented
works to create moir\'e patterns have been focused on a twist embedded inside
channel materials or between channel and substrate. However, the effects of a
twist inside the substrate materials on the unaligned channel materials are
much less explored. In this work, we report the realization of superlattice
multi-Dirac cones with the coexistence of the main Dirac cone in a monolayer
graphene (MLG) on a ~0.14{\deg} twisted double-layer boron nitride (tBN)
substrate. Transport measurements reveal the emergence of three pairs of
superlattice Dirac points around the pristine Dirac cone, featuring multiple
metallic or insulating states surrounding the charge neutrality point (CNP).
Displacement field tunable and electron-hole asymmetric Fermi velocities are
indicated from temperature dependent measurements, along with the gapless
dispersion of superlattice Dirac cones. The experimental observation of
multiple Dirac cones in MLG/tBN heterostructure is supported by band structure
calculations employing periodic moir\'e potential. Our results unveil the
potential of using twisted substrate as a universal band engineering technique
for 2D materials regardless of lattice matching and crystal orientations, which
might pave the way for a new branch of twistronics.
