Memory drain is identical to mana drain, but it is not blocked by silver. If you are dropped with Memory Drain then you forget the hour before you went down. If you are killed by memory drain, you automatically forget all the events of the day prior to your death. You pull from the death bag as though you always have one additional black stone. Pulling one black stone will give you a death scar and two will make you PD. You always gain a permanent insanity from memory drain deaths determined by the GM.
Memory drain is considered a mental effect, but is only partially stopped by protections such as Resist Mental Effects. They deboost memory drain instead of causing it to fully fizzle.