Wow love the flavor of this card.

I also really like this but: you're asking players to do something they are reluctant to do; Sacrifice lands. The effect is also pretty minimal: I'm essentially sacrificing a land to get a creature and this isn't a great trade off. I recognize there are cards that give you a bonus if you have a land in the graveyard; so long as this theme continues in block then I see it as worthwhile. Without that, I think this should be upped.

There's only one other Rat in the set, so far, so maybe upping the number of rats is a solid idea (and one that would fit in a plane like this.) Any Black tokens made in Soradyne should almost certainly be Rat ones.

But back on topic; maybe this should be X+2 rats, where X is the number of rats you have in play. Or just offer 3 rats per land?

Nlewis loves the flavor, but I'm not even sure what the flavor is.

Under every city there's a rat infestation?

Either way, I agree with Bombshell that something seems a bit off in terms of power. It's a Hill Giant that lets you sacrifice lands in order to make chump blockers. That's like a pizza that I left the cheese off of so that you can drip sauce on your clothes more easily.

Have you not heard of the Pied Piper of Hamelin? The callback to that story felt like fun and the flavor text tying it into the Labs worked well, for me.

The Pied Piper of Hamelin (as I recall) led the townsfolk astray using his beguiling skills as a deviant flautist. He wasn't blowing up the countryside hunting for rats for his experiments.

(Note: Wikipedia tells me other versions of the Pied Piper story involve him turning children into rats. I guess the lands are children?)

No, the story goes that the Pied Piper used his magical flute to summon all the rats from the city and drown them in a nearby river. The mayor then refused to pay him, so the Pied Piper used his flute on the children instead and drowned them.

Don't worry Sean, no need to finish that sentence, I'm just being a joker.

The important thing was that this dude should probably just make 2 rats. The sacrifice at the end is unneeded.

Look, it's not a literal parallel to the Pied Piper, it's just a dirty old guy who goes and catches rats for whatever use they're needed for. The Hamelin reference helps to frame it, but doesn't outright define it. The cost comes from the rats devouring everything in their path, and serves double duty as a resource for the "land in the graveyard / sac a lot of stuff thing that R/B has going on.

I'm thinking my plan is to up the rats to three, or to stay at two and remove the "sac a rat" clause. I don't even remember why I put that there in the first place.

Well, now I insist that this card make children tokens you can drown.

Might not go over well when I cube draft it on the Magic Cruise...

"Hmm... Now, go save your brother!" Tosses him into the lake also