The first three sections are pretty self-explanatory. My Gear shows you what you've unlocked, including visual representations of which items have which upgrades; a listing of traps that you have unlocked and which ones you need to spend skulls on to own is under Traps, and a similar listing of weapons are within the pages of the Weapons section.
Trinkets is a new feature, a series of bits and bobs you can purchase with skulls that bestow you with permanent buffs. These are similar to the powers granted by the Weavers in the original Orcs Must Die!; however, these powers won't be level-specific this time. Purchasing a Trinket will allow players to affix extra skills and powers on any map.
Vanity is a section for dress-up, where you'll be able to equip unlockable costumes. In fact, the War Mage's original costume will be one such unlockable outfit.
Each trap, weapon and trinket now has the ability to be upgraded, with each defense item having five to six persistent upgrades to unlock with skulls. Traps have three different levels of upgrades, then two different unique upgrades to unlock – only one unique upgrade can be equipped on a trap at anytime, yet you can unlock both to mess around with each and find your favorite.
The only downside is that in order to equip a particular unique upgrade on a trap, you'll have to purchase it every time with skulls. Finally, some traps will have a "special" upgrade you can purchase. In the example of the Arrow Wall trap, this special upgrade allows players to place the trap on the ceiling.
Fans of the first game may be concerned with all of this skull expenditure. In Orcs Must Die!, 290 skulls were needed to fully upgrade everything in the game, and skulls could only be earned based on performance. In the sequel, skulls are not only earned based on performance, but also as random drops from enemies and as milestones in the game – like killing 500 orcs and the like.