What is the ninth level of consciousness?

Originally, per Pali (Theravada) Suttas, there were only six consciousness taught by the Buddha, as follows:

And what is consciousness? These six are classes of consciousness: eye-consciousness, ear-consciousness, nose-consciousness, tongue-consciousness, body-consciousness, intellect-consciousness. This is called consciousness.

SN 12.2

What is translated above as 'intellect consciousness' includes the consciousness that knows/experiences liberation & Nibbana.

Then later, Mahayana introduced another two consciousness, namely, the defiled (kliṣṭamanovijñāna) & the storehouse (ālāyavijñāna). Wikipedia says:

This eighth consciousness is said to store the impressions (vāsanāḥ) of previous experiences, which form the seeds (bīja) of future karma in this life and in the next after rebirth.

This doctrinal obsession with 'consciousness' obviously came about as Buddhism, including Theravada, developed an obsession with reincarnation. For example, within the Pali Suttas, there is later-day commentary called the Patisambiddhamagga, which introduced the phrase 'relinking consciousness' ('patisandhi vinnana') into Buddhism:

275 . Purimakammabhavasmiṁ moho avijjā, āyūhanā saṅkhārā, nikanti taṇhā, upagamanaṁ upādānaṁ, cetanā bhavo. Ime pañca dhammā purimakammabhavasmiṁ idha paṭisandhiyā paccayā.

In being-as-action before [this life] there is delusion, which is ignorance; there is accumulation, which is formations; there is attachment, which is craving; there is adoption, which is clinging; there is volition, which is being; thus these five ideas in being-as-action before [this life] are conditions for rebirth-linking here [in the present life].

Idha paṭisandhi viññāṇaṁ, okkanti nāmarūpaṁ, pasādo āyatanaṁ, phuṭṭho phasso, vedayitaṁ vedanā. Ime pañca dhammā idhupapattibhavasmiṁ purekatassa kammassa paccayā.

Here [in the present life] there is rebirth-linking, which is consciousness; there is precipitation [in the womb], which is mentality-materiality; there is sensitivity, which is base [for contact]; there is what is touched, which is contact; there is what is felt, which is feeling; thus these five ideas in being-as-rearising here have their conditions in action (kamma) done in the past.

Obvious inaccurate translation by Bhikkhu Ñāṇamoli

When the above subject matter from the Patisambiddhamagga is read & examined in its completeness, there appears no explicit meaning of past & future lives, which is probably why Buddhists monks & scholars rarely, if ever, teach this material from the Patisambiddhamagga. However, later in Theravada, paṭisandhi viññāṇaṁ became another type of consciousness rather than the reunion (paṭisandhi) of consciousness (viññāṇaṁ) with past action/becoming (kammabhava). The fact the term "paṭisandhiyā" is first found above without reference to consciousness shows "paṭisandhi" is not a type of consciousness. All the above appears to say is a present consciousness reunites with a past kamma/becoming, just as a present consciousness today may reunite with a memory & emotion of an act that was performed yesterday.

In addition, what convolutes the matter further is the Theravada Abhidhamma started using the term 'citta' to refer to 'consciousness'. This may have influenced the Mahayana to create the terms defiled (kliṣṭamanovijñāna) & the storehouse (ālāyavijñāna) consciousness.

In other words, from the terminology of the original Pali Suttas, there is no such things as defiled & storehouse consciousness. In the Pali Suttas, there are described five aggregates, namely, materiality, feeling, perception, mental formations & consciousness. What Mahayana calls 'defiled consciousness' equates with 'anusaya' (underlying tendencies) and what Mahayana calls 'storehouse consciousness' is not related to consciousness because consciousness does not store defilements, emotions & kamma. Defilements, kammic imprints ('vipaka') in Pali Sutta Buddhism are included in the mental formations aggregate rather than in the consciousness aggregate.

Then it appears Nichiren Buddhism (now Soka Gakkai) came along with its nine consciousness. In original Pali Sutta Buddhism, this ninth consciousness would simply be the purified intellect consciousness, however, Pali Sutta Buddhism most commonly uses the word 'citta' ('mind-heart') for its descriptions of purification & liberation rather than 'vinnana' ('consciousness').

In summary, the Patisambiddhamagga-come-Visuddhimagga, Mahayana & Nichiren did not really add anything to the original Pali Sutta Buddhism. All they did was rename already existing concepts, and particularly started using the term 'consciousness' ('vinnana') for sankhara (mental formations) and citta (mind-heart) related phenomena.

The word 'vinnana' ('consciousness') refers to 'knowing'. Its does not refer to thinking, kamma, defilement, emotions, feelings & the like. Consciousness only knows. It does not store. It has no tendencies. It has no wisdom. What develops wisdom is the intellect or 'mano'.

But, it seems, because the later Buddhists became obsessed with reincarnation, even though Buddhism teaches there is no soul, they used 'consciousness' as a pseudo-soul; therefore invented their relinking, underlying & storehouse consciousness that travels magically from life to life.

Even though the Buddha explicitly taught there can be no arising of consciousness without sense organs (MN 38), without the other aggregates (SN 22.53), without a mind-body (SN 12.67), the later-day Buddhists created/invented their own ideologies about a consciousness that magically travels around in the vacuum of outer space from life to life; propelled by its stored defilements.