Do you enjoy forcing your opponents to put all their cards in the graveyard so that you can rummage through it and pick the best stuff to use for yourself? The Scarab God does. Would you like to mash two of the best dead creatures together to make something that has the combined might of both? The Mimeoplasm would. Do you want to do all this but you are tired of playing the color blue?

Grusilda, Monster Masher has some scary potential that makes us take a fresh look at creatures and ask ourselves, "What if this creature had those creatures' abilities?"

Five mana for the commander on top of five mana (and tap) for the ability means we probably won't be casting her and using the ability in the same turn. That will probably lead to many awkward turns where we put Grusilda on the board, some combination of imminent doom is loudly existing in our graveyard, and we are nervously waiting for our turn to come again while each opponent decides whether or not to kill her. But if they don't kill her, then something truly magical is about to happen.

Like The Scarab God and The Mimeoplasm, Grusilda has trouble against graveyard exile. One opponent with a Leyline of the Void can ruin her day. Unlike those other commanders though, her ability does not exile the target dead creatures, so if one of her creations dies, she can probably just make another one with the same parts.

Don't forget that all her creations have menace. This is easily forgotten in all the commotion of mad necromantic science, so I'll be reminding you of it a few times.

Entomb

The color black gives us a few ways to Entomb, also known as tutoring a card directly from a library into a graveyard. With Grusilda's abilities, creature cards are more valuable when they are in our graveyard instead of our hand, so regular tutors aren't exactly what we want. If we built the deck with ultra-high mana cost creatures that we were planning on fielding with Grusilda's ability, then we probably don't ever want to have to cast them from our hand the normal way. It's the classic reanimator strategy to cheat the high mana cost creatures out by using low mana cost reanimation effects. If our creatures are expensive enough, then Grusilda's five-mana ability is a bargain.

Mass Discard

If we actively want our creature cards in our graveyard instead of our hand, then it can be beneficial to our strategy to use effects that cause every player to discard. We get to sculpt our graveyard, and maybe one of our opponents discards a juicy creature that we can use. While The Mimeoplasm and The Scarab God might use blue/black Millstone and Windfall effects to put opponent cards into their graveyards, Grusilda gets to use black discard and red Wheel of Fortune tricks. Burning Inquiry is a recent favorite of mine that makes me feel good and my opponents feel bad even though we're all doing the same thing.

There is, of course, a spectrum of how severe you want the discard to be. While I personally wouldn't go as far as Sire of Insanity, I might consider a Dragon Mage to keep things moving. With Malfegor, I'm the only one who discards, but forcing my opponents to sacrifice their creatures does further Grusilda's goal of putting everyone's creatures in the graveyards. Speaking of which, remember to include some of the usual creature board wipes and maybe some Grave Pact effects since they also put everyone's creatures in the graveyards.

Utility Creatures

Evoke

Creatures with the evoke ability effectively give you the option to cast a removal spell at a reasonable mana cost while putting fodder in your graveyard. Since the removal is (usually) in the form of an enter the battlefield effect, we have an option to use that removal again the next time Grusilda makes a creation. These creatures can put themselves in the graveyard for you, so you don't always have to be waiting for one of your discard spells to let you pitch them.

Myriad

There is one particular card that breaks this commander. Once I saw it, it warped the deck building process around it to such an extent that other cards became evaluated, included, or cut based how well they worked with this one card. And the card is... Warchief Giant.

Remember all your favorite black and red bomb creatures that you were thinking about including? Maybe some of them have enter the battlefield triggers, like Gray Merchant of Asphodel, Massacre Wurm, or maybe something with "Titan", "Primordial" or "Gearhulk" as their last name. Hold that creature in your mind... Now, what if that creature had +5/+3 and haste (and menace) so it could attack the turn it appears? Okay, good so far... And then what if, on your combat step, more of those creatures suddenly entered the battlefield out of thin air and were already attacking the rest of your opponents and triggering their abilities right before blockers are declared? That would probably be pretty neat, huh? In the case of most of these creatures, the answer is yes. Yes it would be pretty neat. Even the simple evoke creatures mentioned above would become amazing with myriad. Destroy two target artifacts, creatures, or even lands during each of your combats. Seems good.

If you include Entomb effects in your deck, then Warchief Giant should be one of your early search targets because it makes so many other creatures so much better to a drastic extent. If a creature is a good target for a kicked Rite of Replication, then it's a good creature to pair with Warchief Giant. As a backup, Banshee of the Dread Choir also has myriad as well as some forced discard. If your favorite creature already has haste, then pair that with the Banshee instead of the Giant. That way you can have a second hasty myriad (and menacing) uber-monster on the board at the same time as whatever you made with your Giant. And then Mirage Mirror gives us a third...

Infect

As another option, consider your favorite creature again. Now ask yourself if it would be better with, say, +2/+2, flying, and infect (and menace)? The answer is usually yes. Any creature that can do direct damage to a player suddenly becomes much more threatening if it also has infect. Inferno Titan and Lightning Reaver become poisonous assault weapons. Anathemancer could kill a five-color deck in the late game just by entering the field. Combustible Gearhulk could... let you draw three cards every time, because who would be crazy enough to choose the alternative? Note that if you are going to use infect as a significant part of your deck, then remember to take the Mindcrank out of your mill package because infect damage won't trigger it.

Here's a list of creatures in red/black that have infect. We don't need all of them. If one of these also has another ability like haste or flying or first strike, then I probably put it in my deck. I ended up using seven of these, so if you don't like to use infect, feel free to swap it all out for Gary, Mindcrank, and your other favorite cards that I didn't use. Note that Grusilda making something out of Blightsteel Colossus would require some tricky timing with her ability since the Colossus doesn't like to stay in the graveyard. But yes, it would be pretty neat with myriad (and menace).

The Deck

I consider the two myriad creatures to be auto-includes for a Griselda deck. For the rest of the creatures I am prioritizing haste, infect, discard, forcing opponents to sacrifice, enter the battlefield triggers, and otherwise being great with myriad. If a creature has more than one of these qualities, it gets considered. The non-creature cards are perhaps heavy on the discard, but maybe not. In my opinion, cards that force players to discard are more important to this deck than cards like Waste Not that give a benefit when the discard happens. If we don't include enough forced discard, then Waste Not doesn't actually do anything for us. Due to Griselda's ability cost, I went higher on mana rocks than I usually do for commanders that don't have an ability that costs mana.

Again, if you don't like infect, that set of creatures can be cleanly swapped out for plenty of other things that happen to be spectacular when they have myriad.

(And menace).

Enjoy.