Raises his own max HP.
At the start of battle, Russel forces an enemy into an oath, causing that enemy to take a proportion of damage when Russel takes damage, not to exceed 11% of Russel's max HP.
When that enemy dies, Russel forces another to take the oath.
Russel's ultimate & post-Inferno Flame basic atk marks the enemy. Allied basic atks on this enemy deal extra dmg based on R's lost HP & give R a shield based on total dmg dealt. While shield lasts, R gets extra armor & magic resist.