I recieved this spell last night.
In order to get the mission, not only do you need to be rank 2, but you need medium fame. Which means you need to do other quest.
A party of 6, levels around 20 can easily obtain the Beast blood from a leech in Pashhow Marshlands.
To get to Pashhow Marshlands, you'll need to head south from San o`Doria, to La Thiene Planes. From there you will hit the Valk Dunes. i suggest when you hit the dunes, that you head to Seb (a small city located at the south end of the map between the beaches) to pick up a map. Once you have the map, head to south of dunes to the Highlands, From there you'll head East to Pashow Marshlands.
I do not suggest you trying to solo the leeches, they are very resistant to magic. They assist as well. And be carefull when it rains. Water Elemental comes out. bleh.
I think you'll have more issues with the Medium fame, than you will with this quest.
22 Black mage/11 White mage