All the WarLight Wiki has to say is
In the event of a tie at the end of the tournament, the winner is decided by who won when the tied players played each other.
However, that doesn't tell us who could win in a 3 way tie where they're all level. As far as I'm aware, there isn't a tie-breaker beyond that point. Fizzer should probably look into adding further tie breakers for situations like this.