The Expert battle is just a little harder than the previous event. The mobs have low HP and defense but they hit pretty hard; a good offense will take them out before they can do much damage.

Note that the event shop from the previous event has disappeared, contrary to previous predictions that it would stay up until the start of the 3rd event. I'd planned to buy 2 half-elixirs each day from it, so I end up squandering some materials that I could've used to buy a Gatcha ticket and some more SP. On the bright side, the materials didn't disappear.