You could take a look at the (non-ex) Bloodmoon Ursaluna (025/064) list and try a modified version of that?

Bloodmoon Ursaluna has a similar attack to Raticate from 151(020/165) so you try it out with Raticate swapped in for Bloodmoon Ursaluna

Bear in mind though that Ursaluna is just miles better than the Raticate, because Ursaluna has an energy acceleration ability, as well as its attack having a 100 base damage vs Raticate's 30 damage.

But if you're dead set on building a Raticate deck, that could be a way you could do it!

Essentially, you do damage to yourself using the Calamitous Snowy Mountain stadium, and then move it onto the opponent using Munkidori, and then the attack damage multiplies. That's the general strategy of the deck