Is it confirmed that they've changed ice to resist water? That's a neat change if so, and that terastal definitely looks like the ice one from the icon; not at all convinced it's the water crystal, and I suspect the Pokemon was explicitly chosen to show this off.
The new legends getting Shed Tail seems intimidating, but it really depends what else is in the format and how the sub works. You lose 50% for it by the looks of things, and for the initial meta, the most interesting things to swap to is gonna be... the other cover legend, which will share a ton of weaknesses. Of course, if the sub itself inherits all of that 50% HP, it could potentially make it tanky enough to often take more than one hit. Seems pretty busted still, but we've come to expect that from cover legends, and you'll need some form of healing if it's not just a once-per-fight deal. Unless the move is so strong that people run the pre-evo with 252 HP 252 Speed just to use it, which is very possible. One thing to consider is that if you have something that can outspeed the user and get them below 50% HP, they've just wasted a turn, and I don't think that will be especially difficult to pull off in Ubers when everything and its mum will be carrying an answer to dragon types; if the opponent *does* get their Shed Tail off, you can chunk the Substitute on that same turn and possibly have made the opponent lose 50% on their cover legendary just to get a check in safely; in most scenarios I'd call that a good trade.
I'm not convinced Terastalise will be especially broken, but I also thought Dynamax could be tame so I guess I'm not good at evaluating these things. It has similar unpredictability to Z-moves, but the power is probably gonna be worse than Max moves with no secondary effects, and locking yourself into a typing that can't as effectively use your *other* moves could be really debilitating. I strongly suspect the most common use case will be using it for temporary Adaptability on already very strong moves, or for a temporary way of covering crippling weaknesses like with the Tyranitar example; I'm not convinced that using it to change your STAB is gonna be terribly strong unless there's a way to manually deactivate it. It certainly seems more *interesting* than Z-moves or Dynamax, and I'm impressed they've managed to make a basic concept that is anything but basic in its actual applications.
I like Mirror Herb a lot as a way to punish getting greedy. A big bugbear in recent gens for me has been that it's often actively bad for me to faint an opposing mon, because something else coming in and getting a turn of setup is so crippling, so I can *only* get KOs with things that can deal with that switch in. Mirror Herb provides reactive counterplay to things like that (but in a way that also allows the setup user to play reactively in turn), and should help deal with things like Xerneas in VGC, as well as potentially dealing with some of the more degenerate strategies with Shed Tail. It also means you're losing an item slot instead of a Pokemon slot (Ditto) to punish setup, at the cost of requiring more skilled play.
The new legends getting Shed Tail seems intimidating, but it really depends what else is in the format and how the sub works. You lose 50% for it by the looks of things, and for the initial meta, the most interesting things to swap to is gonna be... the other cover legend, which will share a ton of weaknesses. Of course, if the sub itself inherits all of that 50% HP, it could potentially make it tanky enough to often take more than one hit. Seems pretty busted still, but we've come to expect that from cover legends, and you'll need some form of healing if it's not just a once-per-fight deal. Unless the move is so strong that people run the pre-evo with 252 HP 252 Speed just to use it, which is very possible. One thing to consider is that if you have something that can outspeed the user and get them below 50% HP, they've just wasted a turn, and I don't think that will be especially difficult to pull off in Ubers when everything and its mum will be carrying an answer to dragon types; if the opponent *does* get their Shed Tail off, you can chunk the Substitute on that same turn and possibly have made the opponent lose 50% on their cover legendary just to get a check in safely; in most scenarios I'd call that a good trade.
I'm not convinced Terastalise will be especially broken, but I also thought Dynamax could be tame so I guess I'm not good at evaluating these things. It has similar unpredictability to Z-moves, but the power is probably gonna be worse than Max moves with no secondary effects, and locking yourself into a typing that can't as effectively use your *other* moves could be really debilitating. I strongly suspect the most common use case will be using it for temporary Adaptability on already very strong moves, or for a temporary way of covering crippling weaknesses like with the Tyranitar example; I'm not convinced that using it to change your STAB is gonna be terribly strong unless there's a way to manually deactivate it. It certainly seems more *interesting* than Z-moves or Dynamax, and I'm impressed they've managed to make a basic concept that is anything but basic in its actual applications.
I like Mirror Herb a lot as a way to punish getting greedy. A big bugbear in recent gens for me has been that it's often actively bad for me to faint an opposing mon, because something else coming in and getting a turn of setup is so crippling, so I can *only* get KOs with things that can deal with that switch in. Mirror Herb provides reactive counterplay to things like that (but in a way that also allows the setup user to play reactively in turn), and should help deal with things like Xerneas in VGC, as well as potentially dealing with some of the more degenerate strategies with Shed Tail. It also means you're losing an item slot instead of a Pokemon slot (Ditto) to punish setup, at the cost of requiring more skilled play.
