Oh btw, Japanese-Japanese dictionaries are great for figuring out context/alternative meanings.
For example http://dic.nicovideo.jp/a/%E7%81%AB%E5%8A%9B
It says there that:
Download Links:
Links are hidden from guests. Please register to be able to view these links. So you know it can refer to the power of a martial arts skill as well, not just literal "firepower".
The game in question is league of legends. Oriana is a champion, and her ultimate ability is what I believe the subject of the sentence is (hence the が unless I messed up that particle's meaning). I believe during this time a team fight broke out around the brush(which is what I assumed 草 meant) in the game. It could mean from the brush, since you don't have vision of anyone in the brush without being in the brush yourself and the other team might not of had vision in a brush she ult'd from.
The で's position changes the sentence a lot from the sounds of things.
I didn't even think about using something similar to these yet. But once you mentioned them in your blog(I've started reading it slowly but surely) I realized they could be a very great resource for learning. I'll bookmark one or two and hopefully I'll be able to read what they say sooner or later.
If I knew Japanese I could sort it out for you since I'm well versed in LoL.
Orianna is indeed a champion. Her ultimate is called Command: Shockwave. And yes, brush is a common term in LoL, so you most likely have that translation correct. And you are correct about your game inferences, can't see into the brush unless you are in the brush, or you have the brush warded, or a champion attacks from a brush, they get revealed after attacking.
Sheras have you seen the season finale of SnK yet??