Mahaprabhu's Mission established from the various Vedic Literatures:

** In the Vamana-Purana, the Supreme Personality of Godhead declares:

kali-ghora-tamas-channat
sarvan acara varjitan
sachigarbhe ca sambhuya
tarayisyami narada

O Narada Muni, I will take birth in the womb of Sachi [sachi-garbhe ca sambhuya]. I shall save the people, who will give up all proper good conduct [sarvan acara varyitan], from the terrible darkness of the age of Kali-Yuga [kali-ghora-tamas-channan]. 

** Sri Chaitanya-Upanisad. text 9:

sva-nama mula-mantrena sarvam hladayati vibhuh

The Supreme powerful [vibhuh] Lord Sri Krishna Chaitanya appears in His golden form, and He will fill the universe with bliss [hladayati] by the chanting of His own holy names [sva-nama-mula-mantrena]. 

** In the Garuda-Purana, the Supreme Person says:

kalina dakyamananam
paritranaya tanu-bhrtam
janma prathama sandhyayam
karisyami dvijatisu

In the first part [prathama sandhya] of the age of Kali, I will come among the brahmanas [karisyami dvijatisu] to save the fallen souls, [paritranaya tanu-bhrtam] who are being burned by the troubles of the age of Kali [kalina dahyamananam]. 

** In the Narada-Purana, the Supreme Personality of Godhead says:

aham eva kalau vipra
nityam prachanna-vigrahah
bhavavad-bhakta-rupena
lokan raksami sarvada

O Vipra, in the age of Kali, I will come disguised [nityam prachanna vigraha] as a devotee [bhagavad-bhakta-rupena] and I will save all the worlds [lokan raksami sarvada]. 

** The Supreme Personality of Godhead states in the Narada-Purana:

divija bhuvi jayadhvam
jayadhvam bhakta rupinah
kalau sankirtana arambhe
bhavisyami sachi-sutah

O Divija (demigods), please come and advent as devotees on this earth [bhuvi jayadhvam jayadhvam] in the age of Kali-Yuga. I will incarnate as the son of Sachi [bhavisyami sachi-sutah] to inaugurate the congregational chanting of the name of Krishna [kalau sankirtana arambhe]. 

** In the Markandeya-Purana, the Supreme of Godhead declares:

golokam ca parityajya
lokanam trana-karanat
kalau gauranga-rupena
lila-lavanya-vigrahah

"In the Kali-Yuga, I will leave Goloka and, to save the people of the world, I will become the handsome and playful Lord Gauranga."