Max all abilities:
Successfully complete the indicated task to max out the corresponding ability. Max out all abilities to get the “Jack Of All Trades” trophy.
*Note:* Each ability has 11 upgrade levels. You can view the progress of each ability by selecting “My Career”, then “Abilities” at the at multiplayer menu.
Dark Souls reference:
When the game first begins, look on the walls to find a poster for “Dark Trolls” that features the main character from /Dark Souls/ being chased by a large troll.