Chaos Defiler In formats like Duel Commander, Chaos Defiler shines as one of the nastiest red-black tools around
Once per your turn, when a Spell/Trap Card, or its effect, is activated (Quick Effect): You can negate the activation
For example, if youre using a commander like Gishath that cares about a single creature type, include cards like Icon of Ancestry that let you choose a creature type to apply an effect to, as well as cards that care about your specific creature type (like Thunderherd Migration in the case of Gishath)
The beefy ex Pokemon has a single energy attack that lets you tutor up two Basic Darkness Energy and attach them to Okidogi ex, Poisoning it if you did so
Masterking Archfiend has a strange synergy with Mind Drain it can mill a Fiend with 1000 ATK or DEF if it's on the board when Mind Drain is activated