For the dungeon mechanic, see here.
The resolve leader archetype is based around leader skills with the effect “may survive when HP is reduced to 0“. Leaders with this ability can survive with 1 HP when hit with an enemy attack that would kill while being above a certain percentage of HP; this threshold can range from 40% to 70% depending on the leader.
Note that resolve fails when enemy does multiple hits at once.
Notable monsters of this leader archetype include Viper Orochi
and Great Tengu
.