Corviknight @ Rocky Helmet / Leftovers
Ability: Pressure
EVs: 48 HP / 252 Def / 208 Spe
Impish Nature
- Roost
- Defog / Body Press / Bulk Up
- Brave Bird
- U-turn
This is a fast Corviknight. While it might be less bulky, it does have one thing going for it when compared with the standard set: it doesn't get 2HKOd by banded Stone Edge.
Banded Ttar does 48-56.5% to max/max impish, which is pretty good, all things considered. With Leftovers, that has a 30.5% chance to 2HKO (ignoring the miss chance or the increased crit rate). This makes it almost a coin flip, depending on how lucky you're feeling, and with Stealth Rock up, it becomes guaranteed. So although Corvi did get 4 PP off of Stone Edge, it failed in walling the Ttar.
With speed, though, you can switch in to Ttar no problem. The worst-case scenario says that, after SR, a crit has a 62.5% chance to OHKO. Barring that, however, you will always live (standard damage does 55-64.7%, a crit does 82.5-97.1%). That is, of course, if they even hit.
Each time they Stone Edge, Pressure removes a quarter of their PP for the move. While your lowered bulk means you take more per hit, you are faster than Ttar, and so you can Roost off the damage safely. Not only that, but your Roost means that you will resist the Stone Edge, and you can easily get back to full, even with crits. After 4 Edges, the Ttar will only be able to threaten you with Crunch; this does 44-52%. Defense drops are annoying, but so is Rocky Helmet.
You can also opt for Body Press or Bulk Up on this set, both of which increase your chances of dealing with Ttar. Bulk Up mitigates defense drops from Crunch and helps Corviknight generally against physically-oriented teams. Body Press is an old set, but still could be useful generally, and of course is very nice in dealing with a weakened Ttar (89-105% - forget Roost stalling, just get rid of your problems right then and there).
All this said, I'm not convinced of Corvi's ability to 100% of the time counter Ttar (I always assume my opponent will get all the luck) and so I will classify this as a
check.