Dayana, Selesnya's Vanguard

Whenever Dayana, Selesnya's Vanguard attacks, you can pay {x}{x} to have her fight target creature with endurance {x} or less.
{w} Dayana, Llanowar's Vanguard gains double strike until end of turn
{w/b} Dayana, Llanowar's Vanguard gains lifelink until end of turn
She will protect her new home -at all costs-.