  We present multi-wavelength observations of a prominence eruption originating
from a quadrupolar field configuration, in which the prominence was embedded in
a side-arcade. Within the two-day period prior to its eruption on 2012 October
22, the prominence was perturbed three times by chromospheric fibrils
underneath, which rose upward, became brightened, and merged into the
prominence, resulting in horizontal flows along the prominence axis, suggesting
that the fluxes carried by the fibrils were incorporated into the magnetic
field of the prominence. These perturbations caused the prominence to oscillate
and to rise faster than before. The absence of intense heating within the first
two hours after the onset of the prominence eruption, which followed an
exponential increase in height, indicates that ideal instability played a
crucial role. The eruption involved interactions with the other side-arcade,
leading up to a twin coronal mass ejection, which was accompanied by transient
surface brightenings in the central arcade, followed by transient dimmings and
brightenings in the two side-arcades. We suggest that flux feeding from
chromospheric fibrils might be an important mechanism to trigger coronal
eruptions.
