Simply rolling extra damage dice is so mundane.  

So we made these dice as upgrades to the critical hit system of any tabletop role-playing game. Rolling one of them along with your normal critical hit damage dice will put the “critical” back into your critical hits.

These acrylic 12-sided dice are engraved with graphic results for a critical hit. Most are brutal. A few are deadly.

You might implement these as a full replacement for your critical hit rules or to determine critical hits that are particularly harsh or dealt from a powerful weapon.  

Or maybe you’ll simply leave them on the table and watch your players squirm!