Guild Wars 2

Give him following trait:

“Might of the dying” – barrier you apply to your allies increaes their damage. This effect grows stronger the less percent health they have remaining. When barrier is removed so is the effect.

Affected ally hp 100%-50% – 10% damage boost
Affected ally hp 50%-25% – 17% damage boost
Affected allly hp < 25% – 25% damage boost

If you play it safe and stack barrier on healthy allies you get a little damage boost. If your team takes a risk entrusting their survival to scourge, they get a massive damage boost.

While you wouldn’t get intentional gameplay like that, it is a cool idea. I like it.