Over the course of running Princes of the Apocalypse, the characters spent a lot of time in the Temple of Black Earth and its connected outpost, the Sacred Stone Monastery. When my group first encountered the Monastery, they weren’t powerful enough. They could defeat the gate guards, but that fight left them hurt and needing to rest. So, they would retreat and come back the next day. Meanwhile, the monastery replaced the gate guards – with tougher and tougher foes. And sent some scouts to find the party (the adventurers killed the scouts).
Eventually, getting sick of this, one of the priests in the temple, Qarbo, invited the characters in and explained to them that they were attacking the wrong people. Did they really want to find the delegation? Go bother the cultists in Feathergale Spire. Qarbo even demonstrated a couple of brainwashed delegates to them who told the adventurers that everything was fine.
My group, being extremely easy to lead around, followed Qarbo’s suggestion. Unfortunately for Qarbo, my group was extremely easy to lead around, and so were sent right back to the monastery by the Feathergale Knights. And then they slaughtered Qarbo, freed the prisoners, and took their first view of the temple below – and discovered that it was very dangerous. Thankfully, they retreated and used information from the rescued prisoners to go back to the Feathergale Knights and start bothering them again, eventually leading to their sacking of the Air Temple.
The entrance to the Temple of Black Earth is one of the most dangerous in the adventure. The cult has it very well-defended. In theory, a group of characters who are too low-level will go away and try to find some other way in (as my group did), but the danger comes from the players being stubborn and just trying again and again and again (see above for how my group handled the monastery). One of the biggest challenges in Princes of the Apocalypse is giving the players enough leads and quests so that when they reach a place that is too difficult, they can attempt something different – and letting them know that this is an option. There’s enough material in the adventure so you can do it, but actually conveying that information to the players isn’t always easy.
When my players returned to the Temple of Black Earth, it was from below – from the connecting passages through the Fane of the Eye. This time, they were higher level, but the opposition was still dangerous. There’s a lot of opportunity for the Earth Cultists to attack them from multiple directions. When you’re running Princes of the Apocalypse, it’s a good idea to make a copy of the map, then write on it where each of the groups of enemies are… and then move them in relation to the adventurers as the game progresses. Opponents fleeing from a combat can alert further groups, until the entire complex is alerted and defending against the adventurers. It requires some smart play to overcome the massed opposition.
The most dangerous thing for a group of adventurers to do is to follow retreating cultists. If you check the map of the Temple, there’s a lot of connecting passages and loops. So, it’s very easy for the party to be attacked from both sides at once. It’s definitely entertaining for the DM – and likely the players as well. You want to give the players a feeling of accomplishment, and that works best when they feel like they’re fighting something dangerous. The Temple of Black Earth gives plenty of opportunity for that to occur. In my game, while the adventurers were fighting in area 23, I had reinforcements coming along the corridors from the north and east. The group got the idea in a hurry and fled, though they were able to slay their target.
The other aspect of the Temple that makes it interesting to run is Yarsha (in area B6), who would like nothing more for the characters to murder the second in command, Miraj, for her, so she can become the new deputy, and then to go away. This occurred in my game: she allied with the characters, told them where the “prophet” was – actually Miraj, rather than the prophet – and then laughed maniacally to herself once the characters left.
As it happened, because the characters had already killed the Air Prophet, the real Earth Prophet was down below in the Fane. They encountered and slew him later. However, as I never really told the players that each prophet had his own special weapon (they worked it out later), they weren’t aware of the deception. Yarsha is still down there, but given the characters were eventually successful at closing the nodes, I don’t she’s living the life of power she expected.