In order to win you require to remove your challenger's main guardian, which lags 2 towers which fling damage at your units. You do not require to remove both towers, in truth, you're much better off targeting a single one prior to relocating to the main guardian. Just overwhelm a single tower early on in the match with your Planeswalker, and any quickly summonable units. Summon more units on your Planeswalker's place to strengthen the forces. Once one tower is down, you will have a lot easier time of getting to the guardian - and you truly do not require to go for the other tower unless you actually wish to.