Ancestral Blessing

Do you know how much of a hassle it is to organise Ancestral Blessings for twins? It's horrific. Mother was so exhausted by my eldest she delayed the youngest's by three months, and I don't think I'll ever hear the end of it.

— Exasperated parent

In many Merfolk communities, it is important to maintain the approval of your ancestors. As part of this, a young merfolk requires their approval to officially become an adult in the eyes of their communities. This process of gaining approval is known as Ancestral Blessing.

Execution

When a young merfolk turns 20, their parents or an Elder will reach out to the spirits of their ancestors using Necromancy to discuss the matter of their adulthood. In discussion with these ghosts, a location will be chosen for the young person to sequester themselves in. They do not go in alone, or without aid - a week's worth of food will be prepared by their living family, and the many ancestral spirits will accompany them.
The purpose of this isolation from the living is to allow the youth to speak to their ancestors without any witnesses, so that the previous generations can pass judgement freely. This time can be spent in quiet discussion or in heated debate, depending on the personalities of those involved, with breaks for rest. At any time during this week of isolation, the ancestors can give their blessing to the young merfolk, stating them to be an adult. They are then free to leave, and their adulthood will be confirmed by an Elder. After this, they will celebrate with family and friends, and can begin seeking important community positions.
However, not everyone will get this warm reception from their forebears. For some it will take the full week to gain their approval, and some do not receive it at all. For those in the latter camp, the dwindling of their supplies will eventually force them to leave isolation and admit that they did not complete the Ancestral Blessing. This is a great mark of shame, and the result of this varies. In some groups the merfolk will be exiled entirely, in others they will be taken into the tutelage of the Elders to be trained to be a better person.

Exceptions

For some merfolk, they have a condition that makes them unable to cast the spell required to see the spirits. In these situations, an Elder will cast it for them, and wait at a distance from the isolation space so that they cannot overhear the discussion. When the spell inevitably wears off, the youth is allowed to exit and speak to the Elder to have it reapplied, usually in the morning of each day of isolation.
For others, it may not be possible for them to communicate on their own due to disability. For them, their adulthood 'isolation' may come with an aide, which may be an Elder and/or a close living relative. It is more important that you receive your ancestors' blessing than that you are alone for it, after all.

Planar Magic by Isaac Thompson