  We present optical observations of the Type I superluminous supernova
(SLSN-I) SN2017dwh at $z\!\approx\!0.13$, which reached $M_{i}\!\approx\!-21$
mag at peak. Spectra taken a few days after peak show an unusual and strong
absorption line centered near 3200\AA\ that we identify with Co II, suggesting
a high fraction of synthesized $^{56}$Ni in the ejecta. By $\sim\!1$ month
after peak, SN2017dwh became much redder than other SLSNe-I, instead strongly
resembling broad-lined Type Ic supernovae (Ic-BL SNe) with clear suppression of
the flux redward of $\sim\!5000$ \AA, providing further evidence for a large
mass of Fe-group elements. Late-time upper limits indicate a $^{56}$Ni mass of
$\lesssim 0.6$ M$_\odot$, leaving open the possibility that SN2017dwh produced
a $^{56}$Ni mass comparable to SN1998bw ($\approx\!0.4$ M$_\odot$). Fitting the
light curve with a combined magnetar and $^{56}$Ni model using ${\tt MOSFiT}$,
we find that the light curve can easily accommodate such masses without
affecting the inferred magnetar parameters. We also find that SN2017dwh
occurred in the least-luminous detected host galaxy to date for a SLSN-I, with
$M_{B} = -13.5$ mag and an implied metallicity of $Z\!\sim\!0.08$ $Z_\odot$.
The spectral properties of SN2017dwh provide new evidence linking SLSNe-I with
Type Ic-BL SNe, and in particular the high Fe-group abundance may be due to
enhanced $^{56}$Ni production or mixing due to asphericity. Finally, we find
that SN2017dwh represents the most extreme end of a correlation between
continuum shape and Co II absorption strength in the near-peak spectra of
SLSNe-I, indicating that Fe-group abundance likely accounts for some of the
variation in their spectral shapes.
