God for His mercy, what a tide of woes
Comes rushing on this woeful land at once!
I know not what to do. I would to God,
So my untruth had not provoked him to it,
The King had cut off my head with my brother’s!
(Act 2, scene 2, lines 103–107)

Before he leaves for Ireland, King Richard deputizes his responsibility to York, temporarily conferring upon him the powers of the crown. Though York takes this responsibility seriously, the rapidly developing chaos of England’s political situation leaves him stressed and internally conflicted. He knows that he must face down Bolingbroke in Richard’s absence, but he also knows that he lacks the material resources to put up a meaningful fight. Morally unsettled and increasingly irritated with Richard, York reflects that when the king killed his (York’s) brother, the Duke of Gloucester, Richard also effectively neutralized York. This realization marks the beginning of York’s shift in allegiance from Richard to Bolingbroke.

Well, well. I see the issue of these arms.
I cannot mend it, I must needs confess,
Because my power is weak and all ill-left.
But if I could, by Him that gave me life,
I would attach you all and make you stoop
Unto the sovereign mercy of the King.
But since I cannot, be it known unto you
I do remain as neuter.
(Act 2, scene 3, lines 156–63)

York addresses these lines to Bolingbroke, who has just arrived back in England, breaking the terms of his exile. After rebuking his nephew for this action, York admits that Bolingbroke has a legitimate claim against the king for the way Richard defrauded him of his rightful inheritance. Even so, York remains incompletely swayed by Bolingbroke, and he continues to express his allegiance to the king and his “sovereign mercy.” Unable to “mend” the situation due to his lack of sufficient material and political power, York resolves to do nothing and explains, “I do remain as neuter.” In other words, he is both morally neutral and politically impotent.

Fear, and not love, begets his penitence.
Forget to pity him, lest thy pity prove
A serpent that will sting thee to the heart.
(Act 5, scene 3, lines 56–58)

These lines come from the unsettling scene in which York pleas with the newly crowned King Henry to execute his son, the Duke of Aumerle. Having just learned of Aumerle’s involvement in a conspiracy to assassinate the king, York rushes to London to warn the king of danger. York informs the king of Aumerle’s betrayal and counsels Henry not to show mercy. He claims that his son is only penitent because he’s afraid of punishment, not because he truly regrets his actions. As such, if Henry spares Aumerle now, he will simply revert to his treasonous nature and become “a serpent that will sting thee to the heart.” If York is so unforgiving of his son’s betrayal of the king, it may be because of his own guilt at having betrayed the king to whom he himself had sworn an oath of loyalty. He wants to demonstrate the strength of his oath to the new king by refusing to show mercy to his own traitorous son.