Porcus Orcus, once a great friend and ally of the goblins, has chosen to sacrifice them upon the altar of his own glory. Desirous of the title Warlord of Malturrim, he hatches a plan to snatch up all the forces of GoblinTown in one fell swoop. Knowing that the ramshackle collection of hovels has been decimated by raids in the previous days, he sends his sub-chief into town to recruit a few goblins to his forces and reassures the Goblin Mayor of his friendship. Using the recruitment as cover, Porcus and one of his sub-chiefs, enter GoblinTown by means unknown. He waits for the forces of Kris Karnhell, with whom he had crossed paths the day before, to conduct his own raid on the goblins, and in the confusion reveals his master plan: assassinate the Goblin Mayor and take control of all GoblinTown for himself!
To resolve this out-of-the-box plot by Porcus Orcus, we turn our attention to that illustrious tome, the AD&D Dungeon Masters Guide. Porcus is classed as a 5HD creature. The Mayor is classed as a 3HD creature. The conditions are not ideal as the Mayor is on guard and surrounded by his bodyguard. These protective measures are mitigated somewhat by the presence of an ally who stands by ready to assist. All told, this represents a 65% chance of success. The roll comes up 38 - and the Mayor gasps as a blade erupts from his chest and then falls to the ground, slain instantly.
Porcus stands triumphant over the body of the slain mayor and demands the surrender of the town to him, by right of conquest. The bodyguards hesitate...
To determine how the remaining goblins respond to this treachery, we turn our attention to the reaction tables on page 63. The goblins are susceptible to Big Man intimidation tactics, but Porcus now stands alone in their midst. Making a straight roll on the table results in a 68 - "uncertain but prone to positive".
The bodyguards waver. The handful of bodyguards who witnessed the killing of the Mayor level their blades at Porcus, but wait for a command none are willing to give. The largest of them barks out a challenging question, seeking to buy time to think. He doesn't get it as Porcus' lieutenant now strikes at the recalcitrant bodyguard.
Once again, we turn to the assassination table where a 3HD creature attacks a 3HD creature, but striking from invisibility grants Porcus' lieutenant a bonus which bumps him up to 4HD. That results in a one column shift and a 60% chance of success. The dice come up 82 and he fails!
The chief bodyguard hears something behind him, twists about, and runs the approaching orcish subchief through. The goblin bodyguard deftly turns back to Porcus Orcus and grins.
How do the goblins react to this new treachery? Once again, we roll on the reaction table and determine a result of 54: "neutral".
The bodyguard, his blade still slick with orcish
blood, thanks Porcus for his service. A subtle shift in the power dynamics has occurred here, but the new Mayor of GoblinTown is magnanimous. He thanks Porcus for ridding him of his rival to power, then offers Porcus a ten-minute head-start before the Goblins begin their pursuit.
Porcus spits, and snaps out a curse, but he is no fool. He rushes out into the fire and the clangor of Kris Karnhell's ongoing raid and gets lost in the confusion. He narrowly avoids Karnhell himself, choosing to avoid capture by a potential rival for the title of WarLord, in the streets of GoblinTown and clambers over a wall to find safety back in his camp.
Note that these are the publicly known details at this point - for precise information you'll have to ask Porcus Orcus.