Wong is the ceremony that opens Mani Rimdu to the public, held on the full-moon day inside the monastery.
The head lama confers the empowerment of Chenrezig — Avalokiteshvara, the bodhisattva of compassion, whose mantra the monks have been reciting through the closed weeks — on the assembled monks and lay people, and distributes rilwu — small blessed pills, which are what the festival's name refers to — along with tsereel, pills associated with long life. Many people receive a length of blessed cord to wear. Sherpa families walk in from villages across the Khumbu for this, and for a good number of them it is the reason they have come at all: the dances the following day are the spectacle, but the blessing is the substance.
It is held in the assembly hall rather than out in the courtyard, so it is crowded and close, and it is the least photogenic of the three days. It is also the one where a visitor is most obviously a guest at somebody else's religious occasion. Sit at the back, follow what everybody else does, and do not push forward for the distribution ahead of the people it is meant for.
Related Places & Sites

sacred site
Tengboche MonasteryConferred in the assembly hall on the full-moon day that opens the public festival
Deities & Presences
Rituals & Ceremonies
Part of Mani Rimdu