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That's fine.
My plan is to have the skeletons block the tunnel as well as possible and cast black sand where it covers them and the ratlings, causing the rats to take 1d4 damage every round while the skeletons are healed for that much. The area is also shrouded in darkness.
The skeletons then force their way through to block the rats' escape and drive them towards the waiting kobolds, giving them the option to stay in the darkness and slowly die and/or be driven into the 'bolds.
We also really need to get some traps setup in these tunnels for defense, or we're just not doing our jobs as kobolds.