What is unique in the Vodoun ritual is that immortal spirits move among us during votive ceremonies. The Lwas come, they exchange words with those present, they help those that honor them and then they leave.
Lwas are neither good or evil in intention, a western concept that is also mistakenly applied to the rites, Rada would be good and Petro, bad; furthermore, some Oungans would serve with the "good" hand and others, presumably bad, with both.
The truth, as usual, is simpler. Lwas are not better or worse than we are and only with a stretch of imagination will you find the judeo-christian devil in Petro or anywhere in the Pantheon for that matter. No, Rada is air, Danpetro is fire and the two are complementary and intertwine like Ying and Yang, Male and Female. No manicheism here.
Instead, there is more to learn from the families of Lwas and the similarities that cross rite barriers. Case in point, the Agwe family. We have reunited, in this and other families, the Rada, Danwonmen and Danpetro lwas that share name and attributes. We contend that a universal truth hides behind the stereotypic characterisation of our hero-lwa-god. This is not to be confused with the composition of Eskòts, the "teams" of Vodoun rituals. Knowledge of Eskòts is the true secret of a good ceremony and therefore this hands-on subject will not be discussed here, some things are best taught by your spiritual parent during a proper initiation.
Just a hint: Eskòts are like a local sports team, unique, steeped in local tradition but every playing position, from attack to goal-keeping is standard. Every Eskòt will have an Agwe, even in a minor position. To pursue the metaphor, Rites are like an entire sports league, they establish some common rules, set the uniforms and the music but the sporting spirit is the same. Here ends the parable, for you do not choose who your Mèt Tèt is and what rite he or she dances upon, that is your inheritance. But don't see in this a sign that all is written in Vodoun! No excuses, your Nanm is totally yours, you have free will.