Gate Defense is the second optional Story Mission. It introduces the very dangerous Heavy Infantry enemy. This enemy has a large amount of defense, so units without magical attacks will struggle to deal damage to it. At the same time, it has a powerful attack of its own, and low-level healers may have trouble keeping up with it.
Place Katie on the intersection before the bridge (spot H). Afterward place your strongest archer on the lower spot near Katie's left (spot Q). Then place another Archer on the spot above the rock in the center (spot O). Katie's skill should be ready so use it then wait until you have enough UP to place Valerie between the archers (spot P). Next place a Healer on the upper spot to Katie's right (spot X). Next place Cloris on the spot under the rock (spot R), Katie's skill should be ready again so use it to bring in Leeanne on the spot above Katie (spot G). Next place Calliope on the lower spot near Katie (spot Y). Then place Prince near the exit (spot I), Katie's skill should be ready once more so use it and place Eunice on the spot under Katie (spot J). Use the skills of Cloris and Calliope as the Heavy Infantry is in range as well as Leeanne's when she starts blocking an Ogre. Watch Eunice's health carefully as you will need to withdraw him after he has taken a couple of hits.
3★ with level 1 units
Spot notation refers to the annotated map at the top of the page.
Wait until the enemy heavy infantry is nearly engaged with Leeanne. Then activate the following skills in quick succession: Leeane's skill, Valerie's skill, other Valerie's skill, Dorca's skill, Alissa's skill.
Eunice should engage with the second enemy heavy infantry. Withdraw Eunice before he receives a fourth hit from this enemy. (He should receive at least one heal to be able to survive the third hit.)
Wait until the second enemy heavy infantry is nearly engaged with Katie. Then withdraw Katie.
The mages should kill the heavy infantry before it has a chance to hit Phyllis. (If it does hit Phyllis, you can withdraw her and quickly replace with another silver soldier or heavy infantry of any rarity.)