You only need 1 for the monstrology quest. The rest, if you want to make TCs or get xp to level up your monstrology level.
Eventually you will need to get higher level creatures to continue to level up, as creatures too far below your monstrology rank do not seem to give the xp for it.
I have been beating lost souls for a while anyone know how many you have to defeat before you are finished
You only have to do the ONE that was the original quest. The actual intention of doing Monstrology is to defeat several different "Undead" throughout the worlds. Each world has a several variations of "Undead".
For example, in Wizard City, there are, Lost Souls, Skeletal Warriors, Rotting Fodder, and so on. There are some bosses that also count toward the Undead and the ones along with the mobs in Sunken City are included.
After you complete the quest, and return to Burke to finish the quest, you just need to open your backpack. There is a back arrow now, to go back through the items, instead of just forward through all the categories in the backpack. The section with the Animus you have collected is just after Jewels in the backpack, so just click the back button once... or go forward through all the sections to get to it... either way... and you will see which Animus you have collected, and how many for each, and it tells below the picture how many you need for the card, or house guest, or one-shot.
After you complete the quest, and return to Burke to finish the quest, you just need to open your backpack. There is a back arrow now, to go back through the items, instead of just forward through all the categories in the backpack. The section with the Animus you have collected is just after Jewels in the backpack, so just click the back button once... or go forward through all the sections to get to it... either way... and you will see which Animus you have collected, and how many for each, and it tells below the picture how many you need for the card, or house guest, or one-shot.
Hit the "t" key, this brings up that page without leafing through your journal.
Next to the badge tab there is a tab that shows fishing, gardening and monstrology levels. It will show what level you're at. If you put the cursor over it it will show how many xp you need to go up to the next level. Just keep fighting harder and harder undead as you level up so you will get more monstrology xp. I fought in Krokotopia, Mooshu and Dragonspyre as I have progressed.
More feedback: I couldn't find the Monstrology tab again. I went through the tutorial too fast.
I found out online but I wonder how many people will give up on it. Since it's a major new game function I wish it had become a notebook tab of its own, rather than being all the way past 'gems' in the backpack icon tab.
I'm doing OK now btw, all I need now is a handy list of monstrology enemies and where to find them.
It's kind of fun to chip away at it when bored or oversaturated with hard battles.