25 GS Immortal Beloved
Beat the game without dying
While similar to the above achievement, this one means you can't die at all. You die when you are sent back to the previous checkpoint or fireplace. You can get this and the above achievement if you complete the game without dying.
Watch your facial expressions. When your face is basically a skeleton looking face, your next encounter is death. Find small or large health to get you back to normal.
Also, if you die, you would need to start a new game to get this achievement. Starting a new game will erase all previous stats though.
20 GS In the attic, with the knife
Collect the Empty Revolver, Rusty Knife, Bloody Candlestick, Lead Pipe, and Rope
Search every closet, chest, and bookshelf for these items. I found the Lead Pipe in the Mansion Level on floor 2 and the Rope on floor 4. The Bloody Candlestick was found on floor 3 of the Mansion. The Empty Revolver and the Rusty Knife were found in the Attic Level.
25 GS Locksmith's Apprentice
Unlock 50 doors in multiplayer mode
This is a multiplayer achievement as stated. Multiplayer can only be done locally and not over Live. You will need to begin a new game under Multiplayer to unlock this achievement.
10 GS The Bright Side
Use light sources a total of 1000 times
Light sources come in the forms of Matches, Candles, Torches, Lanterns (there are 4: Normal, Red, Green and Blue), Cell Phones, Eye of Sour-on, Flaming Branch, Staff of the Magi-Straight and the Skull of Enlightenment. Cell Phones last the longest but don't give up that much brightness. The Eye of Sour-On, The Flaming Branch, Staff of the Magi-Straight and the Skull of Enlightenment can be used for quick hits on monsters, but they need to recharge, while the others you can only carry a few at a time.
Turn them on for this achievement. I got this on the last level of Catacombs during my 2nd playthrough.
10 GS The Hungerer
Consumed 100 health packs
During your searching, you may get small or large health packs. Find 100 and the achievement is yours.
25 GS Veni, Vidi, Vici!
Escape the mansion after defeating Zachary Graves in multiplayer
As stated, this is done in multiplayer. Multiplayer is local only not over Live. Also, while the last Boss level will be unlocked once you finish the game in Single Player mode, you actually need to play a full game under Multiplayer for this achievement.
10 GS You call this Ocheology??
Kill 50 enemies with a magical light source
Using the Eye of Sour-On, the Flaming Branch, Staff of the Magi-Straight or the Skull of Enlightenment on your enemies multiple times will net you this achievement.