Sewer Syrup himself should be very simple since he's only 64 - 65 compared to your 66 there. The problem would be the aggro... there are many aggroing bats, other slimes, ghosts and undead dogs near that position.
If you could find somewhere safe to pull him (Bind/Grav + Sneak being useful for this), you should easily be able to kill him with Ichi alone, not to mention that he takes extra damage from magic. Susceptible to Slow/Para too.
You could kill the two bats in the hallway and then do the sneak etc pull to the stone passage leading to the Ronfaure exit... it's not -that- far. I'm not sure how quickly he loses aggro though; I've never tried to kite him.
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