Use Ninja and Dancer with maxed out Chicken Knife + 2 Reflect Rings. Dancer in front row. Ninja doesn't matter. Get a few high powered throwing weapons or Fuma Shurikens. Regular Shurikens will work too, it'll just might take longer. Get a Rainbow Dress for the Dancer, too.
I think your only hope is to wait until Omni reflects either Stop or Silence off of you and hopefully successfully hits him. If one of them successfully hit him, Throw the strongest thing you have and Dance ASAP for just that turn. Pray that you get Sword Dance. Or, you could replace Ninja with Monk, and hope for critical hits.
I don't have a single reflect ring, can I get any at this point? Leviathan drops 1+1 in the Sea Trench IIRC, but I don't have access to these until I beat Omni. So, am I screwed?
I don't have a single reflect ring, can I get any at this point?
Yes, you can get Reflect Rings before completing Fork Tower.
They can be dropped by the Parthenope in Phoenix Tower. Plus you can use the Thief Knife to steal them off the Lemure also found in Phoenix tower, or the Fury in the Castle section of the Cleft of Dimensions. ---