Okay, today’s quest actually did call for black spells so I gave in to temptation and built this list. It cost me 4 common wildcards, 8 uncommon, and 1 mythic (for the second Nashi).

The List

Deck
18 Swamp
1 Takenuma, Abandoned Mire
1 Drannith Ruins
4 Gnawing Vermin
4 Okiba Reckoner Raid
4 Cut Down
4 Corrupted Conviction
2 Nezumi Informant
4 Blightbelly Rat
4 Nezumi Prowler
4 Drown in Ichor
4 Sheoldred’s Edict
4 Karumonix, the Rat King
2 Nashi, Moon Sage’s Scion

Sideboard
4 Duress
3 Infernal Grasp
3 Parasitic Grasp
2 Hero’s Downfall
2 Phyrexian Arena
1 March of Wretched Sorrow

20 lands, 20 rats plus the Okiba Reckoner Raids, 12 removal spells, and a little extra card-drawing. Curve tops out at 3 unless you count Nashi’s ninjutsu ability (which you should because it’s awesome). Eight total rares and mythics in the maindeck which you could easily cut down to six because the rare lands aren’t essential.

The Games

I took the deck to unranked Bo1 (so ignore the sideboard, which is very much “whatever I had handy”) and played ten games:

Mono-Red - Win

Karumonix refilled my hand with four rats! Results probably not typical. I stabilized at 10 life and they conceded as I was about to ninja in a Nezumi Prowler to gain some more. This may be a controversial opinion but I don’t think Mono-Red is very good anymore. I haven’t been able to rank up with it and I usually don’t have too much trouble beating it.

Dimir Draw Two - Win

My miser’s Drannith Ruins was actually good here, boosting Nezumi Road Captain as well as an Informant to help put the game away. Then Ruins never showed up again for the rest of the day.

Mono-Green Fat - Win

I kept a removal-heavy hand and they conceded after I killed their first five creatures. If they’d known I had no action to follow up with, they might have stayed in.

Orzhov Toxic Tokens - Win

Karumonix only found a lonely Prowler this time. :( Drown in Ichor turns out to be pretty good in this deck; it transformed a Raid ahead of schedule and delayed their Invasion of New Capenna. At the end they gave me a gift by sacrificing all their other creatures to try to transform Elesh Norn; I cast Sheoldred’s Edict in response.

Plains.dec - Win

They played seven Plains and discarded two more to Informants. If there was anything in their deck other than Plains, I didn’t see it. I don’t think this says anything about the viability of Rats but it was pretty funny to watch.

Dimir Ninjas - Win

They didn’t even bother to leave back blockers when I had lethal on board; guess they had given up. In fairness, as a ninja fan myself, I know how easy it is to get myopic about attacking.

Azorius Knights - Win

They didn’t get a lot of Knight synergy going, unfortunately. Gnawing Vermin milled an Adeline, which must have been a disappointment. Karumonix pulled a solitary Gnawing Vermin. Nashi got a Preening Champion from the opponent. This game was the closest I came to a Toxic victory; my opponent conceded at 7 poison counters with a Drown in Ichor on the stack. They could have chump-blocked for a turn but barring a sweeper would have died to both regular and poison damage the next turn.

Mostly Jund Battles - Win

This was a pretty epic fight. Karumonix got five hits!! I had to discard one to hand size! Then I cast it like four more times and it wasn’t always that good, obviously. They dragged me to the bottom twice. They cast Glistening Dawn twice, once for five and once for eight. Nashi hit twice, but only got a Gnawing Vermin and a land. Drown in Ichor actually made a huge difference, because it put their Invasion of Tolvada out of range of their Render Inert. On the second-to-last turn they made a mistake by blocking my Karumonix instead of my Prowler when they knew I had another Karumonix in hand. If they’d made me choose to cast a duplicate legend post-combat, I might not have had enough attackers to get through for lethal the next time. At the end of the game I had 18 cards left in my library and they had 23.

Selesnya Toxic - Win

I played out more creatures and was able to make an attack that should have been at least slightly beneficial for me no matter how they blocked. They didn’t block, so I slipped in a Nashi and stole one of their Slaughter Singers, which was actually pretty relevant since I had a Karumonix on board! They conceded.

Mono-Red with Urabrask’s Forge - Win

They killed my hard-cast Nashi with an Invasion of Tarkir and sent some Feldons after it, but I kept killing the Feldons. Finally they flipped it with Stoke the Flames and I Edicted the dragon. Less of a focus on getting that dragon might have been the right call against a deck they already knew was removal-heavy. They conceded before I had the chance to get Nashi back with Takenuma. It was a turn early to concede IMO but I guess they were out of gas.

Takeaways

I am not lying to you, I seriously won ten games straight with this stupid Rats deck. At a certain point I told myself I’d keep playing until I lost, but I didn’t lose! WHY DIDN’T I LOSE?? Admittedly, the competition was not top-tier – only the Mono-Red decks and Selesnya Toxic were things I would expect to see on the ladder.

The Toxic plan didn’t really pan out; in most games I wasn’t even close to racking up 10 poison counters. If you wanted to push that angle you should probably find room for more Proliferate effects.

Really, I think my victories say more about the power of running 12 removal spells and having a low mana curve than about the power of Rat synergy in Standard.

This deck has no realistic chance of decking the opponent, so who do you target with Gnawing Vermin? I started out milling my opponent just to get some clues to what they were doing. If the answer looked like it might be “reanimating”, I switched to milling myself.

Should I build this deck?

You should build this Rats deck if you also lucked into opening four Karumonixes and a Nashi or two and feel like they’re burning a hole in your pocket. Otherwise, probably not.