Chapter 13, the martyrdom chapter, tells of the consciousness-raising of bodhisattvas, in which they become envoys of the Buddha by pledging to take the Buddha’s orders seriously as they undergo suffering by working for the realization of truth. These bodhisattvas promised:

Though many ignorant people
Will curse and abuse us
Or attack us with swords and sticks,
We will endure it all.

In an evil age of a muddied eon,
Full of dreadful things,
Evil spirits will take possession of others
To curse, abuse, and insult us.

But, revering and trusting in the Buddha,
We will wear an armor of patient endurance.
We will cherish neither our bodies nor our lives,
But care only for the unexcelled way.

Repeatedly we will be driven out
And exiled far from stupas and monasteries.
Remembering the Buddha’s orders,
We will endure all such evils.
We will go there and teach the Dharma Entrusted to us by the Buddha.

We are emissaries of the World-Honored One.
Facing multitudes without fear,
We will teach the Dharma well.

This section was very moving to Nichiren, who read it as something to be taken to heart and put into practice.

Chapter 13, “Encouragement to Uphold the Sutra,” also teaches entrusting to bodhisattvas the mission of disseminating the Dharma in the evil age, and especially emphasizes the practice of martyrdom by bodhisattvas who are so entrusted. The chapter closes with bodhisattvas vowing to disseminate the Dharma despite intolerable suffering. Nichiren, who suffered many hardships in his life, and his followers, who were also believers in the Lotus Sutra, were encouraged and supported by this exaltation of the spirit of martyrdom, and by the teaching of “the apostles of the Tathagata” found in chapter 10. These teachings also gave them a sense of being among the religious elite and helped create strong bonds of communal friendship. Some contemporary scholars comment that this bodhisattva sense of being an apostle or a martyr is unique within Buddhism.

Because the Lotus Sutra generates such a bodhisattva spirit, some suspect that a distinct group produced it. Even if such a group did exist, since there is no concrete evidence for it, the idea that it existed is no more than conjecture. Rather, the bodhisattva spirit that the Lotus Sutra emphasizes was a radical version of the idea of the bodhisattva way that is generally found in Mahayana Buddhism. So it seems that we need not treat the Lotus Sutra as a special case.

Chapter 12 tells about the future becoming a buddha of Devadatta, the extremely evil one who rebelled against Shakyamuni, and the sudden awakening of an eight-year-old dragon girl. This chapter has been revered since ancient times as an expression of the awakening of evil people and women. While the esoteric Shingon school often uses the term “becoming a buddha in one’s present” it was first used when Zhanran, the sixth patriarch of the Chinese Tiantai school, interpreted chapter 12. The chapter may have been inserted into the Lotus Sutra later and does not form a natural part of the narrative line of the sutra as a whole. Yet, for the reason mentioned above, it is still revered and recited.
Yoshiro Tamura, "Introduction to the Lotus Sutra", p77

[In chapter 11] there is the sudden appearance of the Treasure Stupa, the two buddhas sitting side by side, the gathering together of the buddhas who are embodiments or representatives of Shakyamuni, the united buddha-land, the purification of the Sahā world, and so on. These things were traditionally understood to imply that Shakyamuni Buddha is the Everlasting Original Buddha, and were taken to herald chapter 16, “The Life of the Tathagata.” But chapter 11 also teaches the propagation of bodhisattva practice, which is its ultimate purpose. We can see this in the following:

Who is able to teach the Wonderful Dharma Flower Sutra everywhere throughout this world? Now indeed is the time. Before long the Tathagata will enter nirvana. So that it will last forever, the Buddha wants to entrust this Wonderful Dharma Flower Sutra to someone.

Thus, it encourages actual bodhisattva practice in this world during the latter days and teaches the entrusting of the Dharma to such bodhisattvas.

It is implicit in chapter 11 that Shakyamuni both exists eternally and unifies the bodies of the various buddhas. The Treasure Stupa hangs in the air, with the two buddhas—Abundant Treasures and Shakyamuni— sitting in it side by side. Shakyamuni going to the seat in the Stupa in the air represents the infinite spatial extension of his world. Since Abundant Treasures Buddha is a previous form of Shakyamuni Buddha, their sitting side by side represents the infinite temporal extension of Shakyamuni’s existence. The various buddhas of the ten directions are embodiments of Shakyamuni, which indicates that the true body of Shakyamuni is manifested everywhere. The return to Shakyamuni of all of these embodiments of him as he enters the Stupa indicates that the worlds of the ten directions are unified into one buddha-land. This, too, is intended to reveal that Shakyamuni Buddha is a unifying Buddha.