I'm in the process of making a very story-driven mini-set based around the character of Marthanos, Battle Paladin.
I thought it might be interesting to use the first part of her ability as a cost, since it's something that would generally need to be planned around to be very good. I originally had the card returning to your hand, but I thought that might be too good. I don't know, though. Is it still too good? Is it not as good as I think? Sometimes I have a hard time judging power level.

It's a fascinating ability. I think it's OK. Overrun/Inspired Charge is a pretty powerful activated ability, but it has been on a rare green legend before: Kamahl, Fist of Krosa. Requiring the two off-colours makes it significantly harder to use, which justifies the costs being a bit cheaper. And as for whether the "additional cost" is good or bad, a cost or a benefit... it's a really interesting question. I think this is okay, unless playtesting shows it to be madly broken.