[quote=@ianzerep]
[@BCTheEntity]
Wait, so you're saying that Hidden Strike:
• Works like Download, basin off of the enemy's lower defenses
• Changes type to hit the strongest weakness, basically making it always do ATLEAST 2x damage since every Pokemon has a weakness if ignoring Abilities
• Gains STAB, no matter what
• Breaks through Protect, Substitute, and other moves similar
• Has 100% Accuracy and 90 Base Power.
• Benefits from Priority from Ninjutsu

Forgive me if I say thats pretty FREAKING BROKEN, especially with the base 125 Attacking stats. AG would be holding two Pokemon if such an attack existed.
[/quote]

1. Ninjutsu provides both the +1 Priority and the perma-STAB. Hidden Strike doesn't gain STAB "no matter what", and on most Pokemon would only gain STAB when its attacking type matched up with the user's type (though I could perhaps slightly alter it to clarify that that's also usually what it aims for within any given weakness check if possible); that's just how it interacts with an ability that changes the user's type to match the used move's type. And no, it doesn't ignore abilities that alter resistances or provide immunities.
2. The attack's stats and Protect breaking you described are basically cloned from [url=http://bulbapedia.bulbagarden.net/wiki/Phantom_Force_(move)]Phantom Force[/url], as noted in the move description itself: most two-turn moves such as Phantom Force have power and accuracy around that level, and Phantom Force does benefit from breaking through most moves intended to provide attack immunity, which I figured would be appropriate for an attack where the user basically sneak attacks the target to deal a bunch of damage.
3. Everything else, i.e. Defense/Spec. Defense checking, strongest weakness striking, and 125 Attack and Special Attack, is additional stuff that's not necessarily broken on a Mega Evolution Pokemon, or on the user-created moves that the GM specifically told us to make for stage 3 evolutions such as Megas, and again fits the theme of "ninja sneak attacks a weak point for massive damage".

That said, I'll be fair and admit I'm half-seeing how much Rex will allow with the player-made stuff. Apparently, quite a lot. After some deliberation, including input from another player, I've decided to rework Ninjutsu so that only Dark-Type moves get +1 priority; I've also altered Bombardier to only apply to Fire- and Bug-Type moves, though mechanically speaking, that doesn't actually change much for Mega Volcarona. Moreso for Pokemon who receive the ability via Skill Swap, but...