I'm a little confused on how the new FAQ rules this, but if I have King Balon's Host standing and my opponent gives (let's say) stealth to a character through a card like Lost Oasis, does the character now have one instance of stealth or is that instance immediately removed due to the standing host?

I'm a little confused on how the new FAQ rules this, but if I have King Balon's Host standing and my opponent gives (let's say) stealth to a character through a card like Lost Oasis, does the character now have one instance of stealth or is that instance immediately removed due to the standing host?

Yes. Currently, while King Balon's Host is standing he's applying a constant -1 instance of each (non-immunity) keyword. That means that the stealth granted by Lost Oasis would result in a +1-1=0 instances of stealth, unless the character had stealth or gained another instance of it later.

A standing King Balon's Host removes a single instance of every non-immunity keyword in the game. If the character in question did not already have stealth and your opponent tried to give stealth, it would be ineffective. Your opponent would have to give two instances of stealth in order for the character to have stealth.

If the character already had stealth, then yes, giving that character stealth would overcome the -1 stealth from Balon's Host.

EDIT: Nija'd by Istaril.