The players would only happen upon this, never would they recieve an invite. The chanting can be heard for miles. First, one side will chant, then the other, building up to a climax of some sort. The most signifigant thing of note is the chanting itself, as the two groups have different styles of chants, that seem to have no connection. The first group, the white one if they can see them, has a calm and peaceful trance, almost a sleepy melody akin to gregorian chanting. The second group, the red one, has a much more violent chant, with a deep steady undertone and waves of guttaral war cries, more like an african war chant.
The two sides, once they have been spied, are covered in a paste. There are no designs in it, the paste covers them from head to toe, although there is a wide and clear division between the two sides, one white and one red.
The red side is very agitated. They mill about and collide with one another in agressive movements, shake long wooden spears, sometimes dash around the rear of thier gathering. They gesture and feint, in clearly agressive movement, as if ready and eager for battle. They wear little, only the occasional headdress. There is a semicircle of larger and more decorated people arrayed in a concave facing thewhite side that seem to be leading the chants, and act like swaggering, arrogant thugs. At the focus of the semicircle is a lone warrior, devoid of anything but the paste bodypaint, that is working into a frenzy. He may be twitching and shaking, possibly even foaming at the mouth and rolling his eyes back in his head.
The white side, by contrast, is somehow managing to stay awake. They are standing in place, gently swaying and performing the occasional gentle gesture to accompany the swell of thier chant. From time to time, seemingly random individuals will almost dance a graceful arc through thier gathering, moving with ease and poise, not in a rush but in a measured and soothing path. There is a semi circle of people on the white side as well, leading thier chant. They are calm and have a wizened air to thier statures and guestures. At the focus is a single person, swaying gently and moving with a dancers poise and carriage.
If they are suprised and thier ceramony interuppted, they will scatter and hide, yet keep chanting. A pair will suddenly dash out of hiding, one of each color, running next to each other but not touching. The have a sort of suicidal mindset, so any wounds they recieve, they will ignore, they will run through flames, whatever it takes to reach the threat. When they close the distance, the chanting reaches a climax, the two run together and they explode into a fireball.
If the first fireball doesn’t deter the invaders, other pairs and even groups dash forward to explode. The one side cannot detonate with out the other, this is a binary effect, so if one side is wiped out, they are an unarmed gang in paint. Anyone dead, sleeping, or otherwise not able to keep the mental state the ceramony is created to cause, is unable to contribute to any explosions, even if the other is in the correct mindset.
If they are somehow undisturbed, the ceramony continues as normal, leading the two at the focus to join and anihalate themselves.