# How to shift arrow in diagram

I need to shift this diagonal arrow (in bottom box) down.

``````\xymatrix@R.8pc@C.8pc{
\bullet \ar[rrr]^{i'^{!}} \ar[ddd]_{Th(\Omega_{f'})} &&& \bullet \ar[ddd]^{Th(\Omega_{f})} \\
&&& \\
& \ar@{<=}[ur] && \\
\bullet \ar[rrr]^{i'^{!}} \ar[ddd]_{f'^{*}} &&& \bullet \ar[ddd]^{f^{*}}\\
& \ar@{<=}[ur]_{E_{x}^{!,*}} && \\ \\
\bullet \ar[rrr]_{i^{!}} &&& \bullet
}
``````

What's the problem with writing it like in the first box? I mean like this:

``````\xymatrix@R.8pc@C.8pc{
\bullet \ar[rrr]^{i'^{!}} \ar[ddd]_{Th(\Omega_{f'})} &&& \bullet \ar[ddd]^{Th(\Omega_{f})} \\
&&& \\
& \ar@{<=}[ur] && \\
\bullet \ar[rrr]^{i'^{!}} \ar[ddd]_{f'^{*}} &&& \bullet \ar[ddd]^{f^{*}}\\
&&& \\
& \ar@{<=}[ur]_{E_{x}^{!,*}} &&\\
\bullet \ar[rrr]_{i^{!}} &&& \bullet
}
``````

You can also try a bend arrow:

``````\xymatrix@R3pc@C3pc{
\bullet \ar[r]^{i'^{!}} \ar[d]_{Th(\Omega_{f'})} & \bullet \ar[d]^{Th(\Omega_{f})} \\
\bullet \ar[r]^{i'^{!}} \ar[d]_{f'^{*}} \ar@/^/@{<=}[ur] & \bullet \ar[d]^{f^{*}}\\
\bullet \ar[r]_{i^{!}} \ar@/^/@{<=}[ur]_{E_{x}^{!,*}} & \bullet
}
``````

Also next time please post a fully-compilable MWE.

One can shift an arrow up or down by

\ar@<5pt>[r] \ar@<-5pt>[r]

One can also shift labels, the vertices themselves