This skill is a Special Rule that is only available to specific Star Players. Please visit this page to find a list of current and past Blood Bowl Star Players.
IndomitableOnce per game, when Karla / Willlow successfully rolls to use her Dauntless skill, she may increase her Strength characteristic to double that of the nominated target of her Block action.
This special rule isn’t that special but it may let you get a three dice block on a stronger opponent once per game. Generally even when using Dauntless it is good practice to set up an assist to give you a two dice block, or at least only a one die block if you fail the Dauntless roll.
You might want to save this in case a situation pops up where a particularly troublesome opponent needs to go down, for example a Stand Firm player who is in the way. The extra die on the block might just make the difference. Overall though I don’t think this is one of the more powerful special rules for a Star Player.