D3 branes stretching between webs of (p,q) 5branes provide an interesting
class of 3d N=2 theories. For generic pq-webs however the low energy field
theory is not known. We use 3d mirror symmetry and Type IIB S-duality to
construct Abelian gauge theories corresponding to D3 branes ending on both
sides of a pq-web made of many coincident NS5's intersecting one D5. These
theories contain chiral monopole operators in the superpotential and enjoy a
non trivial pattern of global symmetry enhancements. In the special case of the
pq-web with one D5 and one NS5, the 3d low energy SCFT admits three dual
formulations. This triality can be applied locally inside bigger quiver gauge
theories. We prove our statements using partial mirror symmetry `a la
Kapustin-Strassler, showing the equality of the S^3_b partition functions and
studying the quantum chiral rings.
