As lillia, They are going to be ganking early, and Pantheon can gank early too. Make sure you apply as much pressure to them as you can.

Before invading, make sure you have your Passive stacked so you can win the trade.

If they invade you, be prepared to fight, but only do so if your Passive is stacked and you can win, otherwise just back off.

Post 6, they win the 1v1 as they’re stronger when their Ultimate is up.
 As lillia, Before invading, make sure that you have your passive stacked so that you can win the trade. If they invade you, be ready to fight, but only do so if your passive is stacked and you can win, otherwise just step back. Post 6, they win the 1v1 as they are stronger when their Ultimate is in place.