Buff Knight Advanced

This is more than likely the last trophy you will be going after as it's the most time consuming of all the trophies. The description is a little misleading as you do not need to collect 20 artifacts, but all 20 artifact TYPES. You get artifacts by beating bosses and occasionally enemies drop them after being killed during the stages themselves. Which ones are dropped are random so there's no knowing what you are going to get for the most part when you find one. There is a total of 20 different artifact types (note that these are not their maxed levels, just what they look like):
 

You are able to upgrade them as well by collecting multiple copies of the same artifact as they go up one level for each additional one you get until they max out at level 10. One you obtain all 20 artifact types and upgrade them completely, the trophy will pop.