If you have 3 "Fatal Abacus" and 2 "Coffin Seller", each monster sent to your opponent's grave from play for any reason will cost them 2,100 LP. Swap at least one "Coffin Seller" for at least one "Dark Room of Nightmare" to make the 3 Fatal Abacus deal either 2400 or 3,300 damage per monster. (Making it possible to have an open zone for a protective Magic/Trap card).
If your opponent has 3+ monsters on the field, and you have a Cyber Jar set with one of the above combinations ready, you can OTK your opponent for 8,400-16,500 damage.
You can avoid the negative effect of this card by using Trap Monsters since you will only receive damage if they are considered monsters both on the field and in the Graveyard.