The Vahki squads that we see sneaking through the metrus of the city today have a long line of history in their creation and designs. The Vahki that you see today did at one point look much different, in size, strength, and intelligence. Turaga Dume had originally had his own ideas for the Vahki enforcers, but they were eventually changed with the help of Toa Lhikan and the matoran.
Although this creature may resemble a Rahi, it is in fact purely robotic. It was the early design prototype for the Metru Nui order enforcement squads, and perhaps two dozen of these were built. Its tail launches an energy bubble which it can completely enclose an offender. The prototype then drains energy from its captive into itself, leaving the lawbreaker too weak to cause trouble for quite some time. They were eventually "retired" in favor of the more efficient Vahki, but these beings refused to be shut off and are believed to be hiding in some of the less-frequently visited sections of the Onu-metru Archives.
The newest version of the Vahki squads are however, much more efficient then their older Kralhi counter-parts, and now equipped with speical "stun staffs" that after use leaves the offender helpless, and unable to cause trouble around the metru for a while. Matoran now a days fear the Vahki for their very dangerous and mean nature to the matoran, and even worse to the rule breakers! Some matoran who are so afraid of the Vahki, look out for them and tell on other matoran who are doing offenses to the city, making some very unpopular to other matoran of their metru.
