When dealing with top-tier villains it is important for Game Masters to establish ground rules early on as to how these entities can be dealt with. That doesn’t just mean how they can be defeated. In all likelihood they may be so powerful that they can’t be defeated by the players under any conditions. However they can be be interacted with on some level and the GM has to set in stone the kinds of interactions their players are allowed to have and what the consequences of those interactions might end up being.
By way of illustration we’ll use an existing entity from my own game. This being is based upon the Monstrous Compendium entry for “Solar Aasimon”. Those familiar with this entry will recognize it as the single most powerful creature in the entire collection. Categorized as “Celestial Stewards” they are essentially the equivalent to angels. The primary difference between the Solar Aasimons and the entity in my game is that Solar Aasimons are uniformly good in alignment. My top-tier villain is not. They are also more powerful than Solar Aasimons because of their backstory and subsequent slide into evil behavior. Needless to say the players in my game would not fare well against this opponent in their current condition. Even when they manage to level up to 30th level (the current maximum for levels in my game) they are still going to have one helluva fight on their hands.
The ferocity of this fight is only going to be made more frustrating by the fact that this entity cannot be slain by anyone short of a proper deity. This is because at this level the struggle between good and evil is the overarching saga that forms the essential base for everything else in the game. The powers of a fallen angel pitted against the ultimate force of good in the multiverse is the backbone for everything the players have encountered up to this point and everything they are yet to experience. Force of arms and magic are insufficient to deter the overwhelming strength of an evil this pervasive. It can’t be banished, vanquished, imprisoned, throttled or backstabbed. So how can the players overcome it?
The short answer is that they can’t. The longer answer is that they don’t need to. There are some basic principles that the entity must follow because even they exist in a system that is beyond their full control; they are not a god and therefore have limitations inherent to their reality. First, they cannot simply attack somebody without provocation. This does however mean that they can determine what is a provocation and what isn’t. If the players show up to meet with this entity and one of them is wearing a sword, that may be seen as a provocation. Or the entity might see it as a provocation only if the sword is drawn. A fair amount rests on the players. The entity may feign outrage at the mere presence of the sword as a ruse to cause the player to then draw the weapon, effectively crossing the line without the entity having to have made the first offensive move. As a further example see every western movie ever made in which a gunfighter fakes out an opponent in order to shoot them down in “self defense.”
The second limitation is that the entity cannot be in two places at the same time. If the players know for a fact that the entity is in one place then they can rest easy that they are not in another. Of course the entity can teleport without error in an instant to any other place so this doesn’t really amount to any true measure of security.
The third limitation is that the entity, as powerful as it is, cannot create a living, sentient being. Naturally there are work-arounds to this as well. They can create illusions of others or even themselves to frustrate opponents. They can animate the dead and set them to all manner of shenanigans. They can summon living creatures too, so while they didn’t create them out of nothing they can still unleash them on those that irritate the entity. Most devastatingly though they can summon forth more fallen aasimons that can themselves assume the identities of souls removed from this plane by the death of their mortal form. Through deception and deceit this entity manages to take hold of and wield more power than they actually have. Players will need to be skeptical to a degree that they have yet to display in order to effectively negotiate their way around this entity should they decide to stand in the way of the player’s schemes.
Lastly there is a word of warning. None of the limitations placed on the entity are naturally extended to any of the entities’ followers and minions. The entity cannot just attack the players any old time they want. But they can order their underlings to do exactly that. The entity cannot be in two places at the same time. But they can have spies literally anyplace reporting on everything that is going on. They cannot create life, but they can conjure up infinite minions to mimic the souls of the departed and to possess the bodies of the living in order to carry out the foul designs of the entity. Players need to be on their guard and focus their efforts on more cerebral means of defense when dealing with such forces. This is the most difficult type of interaction for Game Masters and players alike. There aren’t any attack rolls or saving throws that will be of any use. Everyone is going to have to be alert and quick of thought to get out of harm’s way.
Or else they really need to know how to fiddle.