So what does Symbol of the Solari do?

Symbol of the Solari has a replacement effect that applies to a combat if 1) you are the attacker, and 2) the combat ends in a tie because both players have units remaining. Ordinarily this would result in your units being recalled and the defender retaining control, but Symbol of the Solari instead causes all units at that battlefield to be recalled, leaving the battlefield open and uncontested.