Lucifer says hi.
You fight it three times over. First with Celica alone (ilu Nil Dynames support you should have my babies many times over)...
Next with Ekria and Celica's party...
And lastly with Louie and company (I hate how they made it seem like Louie and co. were the cleanup crew, wtf)
I forgot to mention, but during the entire fight, that thing was spewing out little (in comparison) baby dragons as well (as you can see in the pic with Celica). Other characters were fighting those mini dragons in the meantime.
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It was reminiscent of the Majin rush fight early on in VERITA, which I loved to death because those were the Hagure Majins in previous games! And they get to try and kick both party's asses one after the other!