His passing
I said:
I'm curious - how did Bah'u'llah die, and are there any particular traditions associated with regards to what happened after his death (ie, to Bah'u'llah particularly)? If it is not a silly question, is his person, spirit - even soul - ever invoked in Baha'i belief?
It's refered to as His Ascension.
It's a Holy Day to Baha'is.
Here's an ouline of events lifted from _God Passes By_...
Ascension of Bahá'u'lláh
Well nigh half a century had passed since the inception of the Faith....
Already nine months before His ascension Bahá'u'lláh, as attested by `Abdu'l-Bahá, had voiced His desire to depart from this world....
Six days before He passed away He summoned to His presence, as He lay in bed leaning against one of His sons, the entire company of believers, including several pilgrims, who had assembled in the Mansion, for what proved to be their last audience with Him. "I am well pleased with you all," He gently and affectionately addressed the weeping crowd that gathered about Him. "Ye have rendered many services, and been very assiduous in your labors. Ye have come here every morning and every evening. May God assist you to remain united. May He aid you to exalt the Cause of the Lord of being." To the women, including members of His own family, gathered at His bedside, He addressed similar words of encouragement, definitely assuring them that in a document entrusted by Him to the Most Great Branch He had commended them all to His care....
The inconsolable Nabíl, who had had the privilege of a private audience with Bahá'u'lláh during the days of His illness; whom `Abdu'l-Bahá had chosen to select those passages which constitute the text of the Tablet of Visitation now recited in the Most Holy Tomb; and who, in his uncontrollable grief, drowned himself in the sea shortly after the passing of his Beloved, thus describes the agony of those days: "Methinks, the spiritual commotion set up in the world of dust had caused all the worlds of God to tremble.... My inner and outer tongue are powerless to portray the condition we were in.... In the midst of the prevailing confusion a multitude of the inhabitants of Akká and of the neighboring villages, that had thronged the fields surrounding the Mansion, could be seen weeping, beating upon their heads, and crying aloud their grief."
For a full week a vast number of mourners, rich and poor alike, tarried to grieve with the bereaved family, partaking day and night of the food that was lavishly dispensed by its members. Notables, among whom were numbered Shí'ahs, Sunnís, Christians, Jews and Druzes, as well as poets, `ulamás and government officials, all joined in lamenting the loss, and in magnifying the virtues and greatness of Bahá'u'lláh, many of them paying to Him their written tributes, in verse and in prose, in both Arabic and Turkish. From cities as far afield as Damascus, Aleppo, Beirut and Cairo similar tributes were received. These glowing testimonials were, without exception, submitted to `Abdu'l-Bahá, Who now represented the Cause of the departed Leader, and Whose praises were often mingled in these eulogies with the homage paid to His Father....