What Does Oathbreaker Do?
Oathbreaker has the Lifesteal ability, but more importantly she also buffs other characters that also have Lifesteal: every time she attacks, all your Lifestealers on the battlefield gain a permanent +1/+1 buff.
That doesn't just mean that they're stronger fighters. It also means that the amount of life they steal is greater, allowing you to potentially build up a much greater pool of health.
Oathbreaker clearly works well with 'vampire' style decks based around cards with Lifesteal. The addition of the Omens of the Past Lifeforce mechanic gives more options to such decks.
This page written for Eternal version 1.20, Card Set 1
Last updated: 25-07-2017