Venetica

First you must choose to join the Order of the Holy Seal as your guild of choice. Go to the Order's HQ in the Outer City (next to the Judge's house), speak to Rangar, and tell him you wish to join the Order.

Special Note: Joining the Order of the Holy Seal will NOT prevent you from getting the Honorable ending, if that is the one you are going for.

Quest 1
After getting your first quest, head to the Catacombs and go to the crypt (that you probably found earlier) and use your new key to enter it. Kill the skeleton inside an grab the shield from the coffin. Head back to HQ, turn it in, and pick up your second quest from Rangar.

Quest 2
Head to the Inner City and enter the catacombs there. Activate the quest in your journal and follow the marker to the crypt. Enter and grab the item. Return to HQ and turn it in. Pick up the third quest.

Quest 3
You will not be able to complete this quest until you gain access to the Arsenal district. Once you do, activate the quest in your journal and follow the marker to a set of stairs near the catacombs area. Go down the stairs, enter the crypt, kill anything in your way, and grab the item. Head back to HQ to turn it in and get your next quest.

Quest 4
You will not be able to complete this quest until you gain access to Africa. Once you do, and you can move about freely, go to the cave containing the Gateway Idol (where Benedict gave you your most recent Mental Power). Dish out some violence and grab the last item. Head back to HQ.

Finale:
Back at HQ you will combine the items you have gathered and St. Anthony will make his appearance. Kill him for his trouble, and be sure to loot his dead self for the awesome sword he carries.

You're done!