This causes the enemy to battle all units not yet on the field. If it wins, all your units are knocked out and the base panel is destroyed. If it loses, it and all its items join your party.
The downsides to this:
- any units of yours the thrown enemy kills count as ally kills
- this new unit is not a student of one of your preexisting units, like if you simply created them as a new character
- you might not get experience for defeating them
Damaging an enemy before throwing them onto the panel may help. The likelihood of subduing them appears to be based on their HP.
Depleting the SP of a monster may also help.
It may also not work against a unit you have not unlocked yet. If they could not be bought for mana they may not be capturable.