The more zodiac coins you give, the more things you recieve. You can find two here in Treno, that should be enough to get you the blood sword. The first is near the entrance, throw money into the fountain 13 times, the second is in the "slums" part of the city. If you have the blood sword equiped to stiener, you obsorb HP when you attack. You might also want to have the auto potion ability equiped if you plan on fighting the monster.

Basically your original question was already answerd, so... this is just a little extra I thought I would add.