How about this: the Jovoc railgun!

You get your wizard that can summon 64 of them at a time.

I am assuming that these Jovocs are pretty strong...I cannot find my MM2 anywhere!

You summon them in a line while moving backwards on your phantom steed.

Each round your line increases by 64 jovocs. Each of them ready an action to pass along anything the previous jovoc hands to them, and then the last Jovoc jumps into the arms into the jovoc immideately in front of him's arms.

The Jovoc will be doing lots of damage (I dont really know how to calculate it...lets just say 20d6 damage) and blowing up. This is a siege weapon. One of these can level an entire castle. As the length of the line gets longer, the speed gets faster. Because of the fact that after you have 64x23 jovocs they will start dissapearing, you probably wont reach escape velocity. Or you might...who knows. Nevertheless, you can probably hit a castle a fair distance away with something that will blow the entire thng to smithereens...actually, it will take a few jovocs to destroy a well built castle, but just one would kill everyone inside.