LogFAQs > #971309168

Calwings posted...

Windsweep = If unit initiates combat with a sword, foe may not counterattack. You need an S-rank Bond Ring of Alm to give a unit that skill.

https://serenesforest.net/engage/miscellaneous/skills/
https://serenesforest.net/engage/weapons-items/bond-rings/

In normal gameplay it only lasts one battle, but the arena is basically extending one battle until one of the units loses. Essentially, the game got stuck in a situation where Lapis couldn't do any damage to Louis, but Louis was prevented from counterattacking due to Windsweep. The battle would never end and you'd be softlocked, so I guess the game is programmed to call the battle a draw if it goes too many rounds without either unit losing. Theoretically, I guess this could happen without Windsweep too if the armored unit with high def simply had a 0% chance to land a hit.

Yeah I imagine it's mostly to stop situations where both sides can't hurt the other or can't hit the other. I never considered Windsweep because I thought Rings weren't active in the arena.