Making The Undead

[frogglesmash]

While Animate Dead, Create Undead, and Greater Create Undead allow an aspiring necromancer to create a large variety of undead abominations, it's always bothered me how so many more undead there are that can't be created (by players)
Of course I recognize that some undead only occur spontaneously, through the creation of spawn, or whose origins are unknown, but there are a shocking number of undead that are described as being created through necromantic rituals, but all too often these rituals are never explained which leads me to my question/request. How would one go about designing the specifics of these rituals in a way that is balanced and fun?

[GnomishPride]

What I like to do is approximate the spell (and appropriate CL required) to create that undead.
Since a lot of undead were designed after Create (Greater) Undead were designed, I choose to assume that had those undead should be on those spells able-to-create list.

Hope this helps (brief though it was).
Might post more later.

[OldTrees1]

Those (balanced and fun) are both subjective judgements so the best I can do is give a personal preference answer:

As the player, I would like to be challenged to design a thematically appropriate setup that was then powered by Create Undead (with a spell slot level requirement).

The rituals would fall in 2 categories
Prepared death: Uses a living being as a subject. The death of the subject under the conditions provided by the ritual will cause it to rise as the intended undead rather than truly die.

Infuse corpse: Uses a corpse as a subject. The ritual is used to create/birth the necrotic spirit the specific type of undead needs. The spirit is then channeled to animate the corpse as the desired type of undead.

Mechanically IC: It would require off screen time to gather the ingredients, the setup and the ritual would take an hour at a specific time of day(beware Pelorites), and the ritual would involve some skill/caster level checks for the satisfaction of demonstrating skill with a small chance of "came back wrong".
Mechanically OOC: it would require naming some thematically appropriate ingredients, rolling the skill/caster level checks, and casting Create Undead from a high enough spell slot(better gate than a minimum caster level).