In the battlefield in Lanka there were only three major enemies:
Ravana, Kumbhakarna, and Meghanada.

In spite of his boons from Brahma, Meghanada always took care not to cross paths with Hanumanji.

Hanumanji punched Ravana once.
Ravana fell unconscious.
Same with Kumbhakarna also.

The confidence of the vanara-sena in Hanmanji's power was so much that once when a lot of prominent vanaras were wounded including Jambavan, Jambavan asked Vibhishana:

Who all are still alive?
Is Hanuman alive?

Yes, he is alive.

Then there is no worry.

If Hanuman is alive, he will revive all those who have died also.
If Hanuman is not there, then there is no point in others living anymore.

Of course, this statement excluded Lord Rama and Lakshmana.

Ravana was in the battleground on his chariot.
Hanumanji requested Lord Rama to sit on his shoulder and fight so that they could be at an equal level.
The Lord obliged.

Meghanada had obtained a boon from Brahmaji that he can be killed only by someone who has not slept for 12 years and observed brahmacharya also throughout that period.

Meghanada thought there can't be anyone like that.

But Lord Lakshmana had already undertaken this tapas during the vanavasa itself.

When Meghanada realized this, he knew that his slayer has come.

He focused all his power on Lakshmana.

He had obtained another boon from Brahma in the form of a weapon.
It's a lethal poison.
It can be used only once.
In the most difficult situation, when the death of Meghanada becomes certain, then he can use it upon the enemy.

If hit by that weapon, if the enemy is not detoxified before the next sunrise, then no one can save him.

Meghanada hit Lakshmana with this weapon.
He fell unconscious.

It was a dangerous situation.
Meghanada wanted to take him away but he could not lift Lakshmana's body.

In the meantime, Hanumanji lifted Lakshman's body and took it near the Lord.

The Lord was in deep pain when he saw Lakshmana's body.

Hanumanji could not bear to see the Lord's pain.

Hanumanji lifted a huge mountain and ran towards Meghanada.
Meghanada jumped down from his chariot and ran back to the palace.

Hanumanji did not chase him because he had to get back to Lakshmana to save him somehow.

Hanumanji was in rage.

He assumed his original form
His body was so brilliant as if flames were coming out of it.
You won't be able to look at it for more than a moment.

Hanumanji said: my lord, please command me.
I will get amruta from wherever amruta is there in Nagaloka, I will crush the nagas under my feet and get it.

Amruta is there in the Swargaloka.
Even Devendra and his whole army will not be able to stop me.
You just order me, I will get it.

Or the critical period is till sunrise.
Before sunrise Lakshmana has to be revived.
I will catch hold of the Surya bimba and throw it into infinity so that Sun never rises again.

It is death, isn't it?
I will kill Mrityu himself so that he will not be there to take Lakshmana's life.
Just tell me what should I do.

The Lord said: get Sushena here.

Sushena was the vaidya of Lanka.
Even though he belonged to the enemy camp, he observed vaidya dharma.
There is no friend or enemy for the vaidya.
A patient is a patient, it is his duty to treat.

It was nighttime.
Hanumanji went into Lanka.
He didn't know how to go about bringing Sushena to the battlefield.
Will he listen?

Hanumanji just lifted Sushena's house, brought it, and placed it in the battlefield near where Lakshmana was lying.

Sushena was a Rakshasa, nishachara, very much awake.
He opened the door, came out, understood the situation, and went straight to Lakshmana.

He examined Lord Lakshmana and told Hanumanji:

Time is running out.
I need five herbs.
Go to Manasarovar.
Between Kailasa and Rishabha parvata you will find Dronagiri.
It can be easily identified because the medicinal herbs on Dronagiri will be glowing in the night
From Dronagiri get me Sanjeevani, Vishalyakarini, Vranaropini, Suvarnakarani, and Sandhani.

Hanumanji immediately took off towards Dronagiri.