Dark Souls could well be the hardest (and most rewarding) video game you'll ever play: a grueling action-adventure about a hero who storms through gloomily lit castles and caverns, smashing, skewering and sometimes setting alight enemies who, upon dying, relinquish souls. Those souls, which manifest as hovering points of light, whoosh toward you like fireflies drawn to a bug zapper, filling your pockets with eldritch currency. If you die before spending it on upgrades, you lose it all, making Dark Souls a game of wagers, or "gothic-flavored investment banking." Do you push forward or turn back, breaking stride, to cash out before trying again? Call it gaming on tenterhooks, an improbably satisfying experience drizzled in dread — a return to form for gamers who relish playing on tightropes, net-free, wrapped in a gorgeous, alien ax-murdering otherworld.