The Worldwound Incursion
Home campaign rules: PCs built on 25 point buy, with a special Session 1 Only option to try to roll up even better characters. New races allowed are half-dragon, half-drow, half-dwarf (mul), and half-ogre. Mongrelmen were added once the party met and befriended these creatures. The classes allowed are all Core Rulebook classes plus gunslinger, magus, and witch. Characters begin with 200 gp to buy equipment. Characters have two traits, one of which may be from any Paizo rulebook, the other of which must be a campaign trait from Worldwound Incursion. Experience points awarded based on expected level progression as shown in the front of each module, not encounters. The year in 4718 (to match the Real World year), so it is a little different than the default for the adventure path.
Mythic adventures home campaign rules: Non-mythic PCs begin with 3 pre-mythic power uses which they can use to surge, stabilize, and save themselves and their allies from death. These points replenish every session for pre-mythic characters (and once per day for mythic characters, or faster, depending on tier abilities). Surge is a free action that may be taken at any time, even if it's not your turn, even if you are incapacitated or otherwise unable to act, though not if you are dead. Surge adds 1d6 plus half your mythic tier to any d20 roll by yourself or an ally. Once you surge, no one can use mythic power or other abilities to influence the roll further. For one mythic power, as a free action, stabilize yourself or an ally (once you are mythic, you no longer need to stabilize yourself). For two uses of mythic powers, convert death of yourself or an ally to brink of death (one hit point away from death, stable and unconscious). There are other changes that will come up in future modules as the party gains power, but for Worldwound Incursion these are the only ones that matter.
The party consists of:
half-dwarf (mul) ranger
half-elf cleric of Iomedae
halfling rogue, later rogue/wizard (universalist)
human wizard (universalist) (joined second session)
mongrelman barbarian (joined later)
half-ogre fighter (joined later)
half-dragon (gold) paladin of Sarenrae (joined later)
The first session had only the first three PC, with the wizard joining in the second session. The setup in Kenabres worked great. The players enjoyed working with the NPCs. The cleric played diplomat, quickly winning the friendship of all three, though the ranger and rogue kept taunting Horgus Gwerm. Anevia Tirabade became their favorite quickly, as she had a helpful disposition and, once the cleric gave her some talk-therapy to mitigate her depression and worry about Irabeth, she was almost a full party member. Aravashniel continually declared himself the wise leader of the party and called the cleric and wizard his apprentices. He quickly connected with the wizard over that character's Riftwarden mark (from his campaign trait) but didn't reveal the significance of this connection until much later. His wand of false life won him the friendship of both the wizard and the rogue (who could Use Magic Device). Horgus Gwerm was the most fun, though. At every opportunity, he made snide remarks, both about the other NPCs and the party members. His insults were paid back many times, and the cleric had to step in over and over to calm him down and prevent Horgus from running off. The other PCs seemed to think this would be just fine, but the cleric wanted to keep the aristocrat safe.
The underground portion of the module played very well. I threw in random encounters at great frequency, since the PCs are high powered compared to the default assumptions of the module. I ran every random encounter at least once before they were through. The bat swarm challenged the party the most, just because at the time they had no good way of fighting a swarm. Once the party made it to Neatholm, they were even with most of the remaining encounters in the underground. A cave fisher gave them some trouble because they only had the scale of Terendelev for levitation and most PCs though they could Climb better than turned out to be the case. Fights with cultists exposed them to fear and Will saves for the first time, which was fun. The final underground fight with some dretches also threw them some trouble, since the stinking clouds affect both visibility and sickness, though luckily the clouds only last a couple rounds.
Initial explorations of ruined Kenabres worked out well. By this time I had a poster map of Kenabres, which helped the party visualize their travels. I plugged in random encounters every chance I could, but the party got to Defender's Heart before I could throw everything at them. They had the hardest time with the invisibility-using, monster-summoning half-orc in the Tirabade residence. As has been noted elsewhere on the forums, this guy's picture is not supported by his statblock, making me think there was a change between what the artist was told and what the final opponent turned into. Also as part of this exploration, the party captured the cowardly Chaotic Evil fighter and tried to redeem him, but he managed to escape when a group of cultists hit the party during transport. They gleefully cut him down, making me wonder about the future of this band of heroes when more chances for redemption crop up.
After reaching Defender's Heart, the party traded Anevia for Irabeth, who welcomed the chance to get back into action (though the couple spent one day together before adventuring). The party mopped up the final cultist bases, eventually tracking the trail of destruction back to the Gray Garrison. At about this time, the mongrelman barbarian and half-ogre fighter showed up and joined the party, followed a session later by the half-dragon paladin. The party did very well in the Gray Garrison, taking two and a half sessions to clear it out, without any escalation of enemy forces (however I did double the number of cultist and tiefling opponents on the second floor, just to make it interesting for this powerful party). I decided the other mongrelmen (rangers) were not needed as part of the exploration party, but joined the defenders in patrolling outside the Gray Garrison so as to keep out reinforcements.
For the final session, the party had reached 5th level. They finished up the second floor with little trouble. I maxed and doubled hit points for encounters with single opponents, just to slow things down. The half-ogre could make quick work of anyone in melee range, so the trick was to keep him shuffling behind the others and squeezing here and there. When he got in range, it was game over for the bad guys. The party ascended to the third and final floor and had a tussle with the fiendish minotaur before the oracle came out. Based on another suggestion from the forums, I wanted her to cast animate dead on the minotaur, but the cleric got a lucky silence spell off on her, and she fell soon after.
The mul ranger struck the wardstone with the rod of cancellation and the final encounter ensued. The party enjoyed the scenes that flickered before them. I used Real Word years to remind them of how long ago various events occurred ("late in the thirties" means the same thing to the characters as it does to the players, for instance). At last, the party received the wash of mythic power as the wardstone net collapsed, transferring its energy to them. They saw the gate into the Abyss and all the armies of demons waiting to storm in, just for a moment before the gate collapsed and only the babaus remained. I didn't increase the number of these demons or add a vrock (as others have suggested). It turns out that these demons had virtually little hope of getting through the party's temporary DR for more than a scratch here and there, except when they used teleport to position themselves and then four of them flanked and sneak attacked the half-ogre, bringing him to unconsciousness. Still, the cleric revived him, and the party proved victorious.
The module lasted ten sessions and ended with the party just reaching 6th level/1st mythic tier. This is the third time I've run an Adventure Path starting module, and all three times it's been a great experience (the others were Rise of the Runelords and Second Darkness). The previous Adventure Paths eventually petered out (module 6 for RotRL and module 5 for SD). This time I think I can keep the campaign going through all six modules. I have some experience with Mythic Adventures and, with some easy modifications, I think the "new" options in that book can keep the players interested in this path clear to the end.