2. Make Dungeons really dark.
3. Put traps everywhere.
4. Add a ton of Undead enemies.
5. Proceed to crap pants.
Now amirite or amirite?
4.c. insert Necromancer or similar faction with backstory, character dialogue and quests that are actually scary
4.d. overhaul ghosts, undead to make them actually scary
4.e. remove any enemy NPCs talking shop about mudcrabs from dungeon
4.f. more cramped, claustrophobic caverns, esp. where you must sneak past creepy enemies that can easily kill you
4.5: Take a hint from MMM and let some undead reanimate and surprise you from behind, when you thought that you have disposed of them.