Soul Link:
Cost: 4
Demonology Hero Required
Ongoing: Put 1 damage on an ally in your party-->Prevent the next 1 damage that would be dealt to your hero this turn.

Ya'mon:
Cost: 4 Attack: 4 Health: 6
Ya'mon has +1 ATK for each damage on him.

So, I was recently thinking of all the fun things I could do with Soul Link, when I thought of something rather spectacular (to me)
I read Soul Link as if it says I don't have to have damage coming at my hero to put damage on my allies. I could (potentially) play Ya'mon, then put 5 damage on him from Soul Link to put a "bubble" around my hero that would prevent the next 5 damage, and then (with ferocity, or waiting a turn) hit with Ya'mon for 9, right?

If this is possible, how long would the "Prevent 5" stick around? Just till the end of my turn, or until it is actually used up? If it stays till it is used up, couldn't I just "kill" an ally every time they try to with a spell and build up a huge shield?

As the card says:

"Prevent the next 1 damage that would be dealt to your hero this turn"

So the bubble will last until the end your turn.

so it sounds like your idea of whenever a spell is coming at an ally just pumping it full of damage would work, the protection on your hero just wouldnt stick around past the turn... still sounds decent though

Though is there a way to use this tactic in combat and still have your ally return damage?

It depends: If you destroy the ally through Soul Link, then no it wouldn't work. But, if they are about to kill the ally anyways I do things like this:

Playing against another warlock with an Infernal out. I had a Fa'tafi, and their Infernal declared an attack against Fa'tafi. Just to be safe, I put 5 damage on Fa'tafi so I could stop the next 5 against my hero (just to be safe) then the Infernal's attack went through, and the Fa'tafi still hit back for 3 before becoming destroyed.