It is unwise to summon these spirits, because they are unquiet and they will cause us unquiet. Some do this because they cruelly and opportunistically want to use the power of these disembodied angry, confused, grief-stricken Souls to nefarious purposes. It never ends well. This is most true if one attempts to use the power of a Child who died in unhappiness. Though they are the most powerful Spirits, they are no more rational or dependable after they have died than Children are in life and one will most surely find oneself dealing with a very angry, confused, grief-stricken Spirit that seeks revenge and cannot be reasoned with and becomes as demanding as Children who are alive do, and just as "stuck" on you.
Spirits like these, when they allow themselves to be seen, usually very quickly, are often misshapen or amorphous precisely because they are thoughts and feelings, and even lives, that never reached their fulfillment. It is as cruel to recoil from them in horror as it is to recoil from a living person in a misshapen body.
The correct relationship to the world of occult spirits is to develop Compassion within ourselves generally. In this way, we will act with Compassion in our everyday lives and any Spirits that attach themselves to us in hopes of finding fulfillment and peace will, de facto, do so without our relating to them directly. It is unwise to consider the occult or interact with disembodied Spirits directly. Let us get on with our Lives in the present. We may be sure, if we do, that any sadness from the past that is relevant to us will be laid to rest as a natural matter of course through our Compassionate actions.