This skill makes your golems much more useful in the long term. A speed increase, a damage increase and a hit point increase. A few points should be put into this skill for a Necromancer that uses golems, however as you will probably end up with many +skill items it is probably not necessary to invest in it all the way up to 20
Developing this skill permits the Necromancer to divert more of his will and energies into his artificial creations. This allows the Necromancer to create more robust golems and control them with greater finesse.
↑Diablo II Manual, page 76. Blizzard Entertainment, 2000.