Slaying Stone Skill Challenges

In threads about The Slaying Stone on RPGnet and ENWorld, and in a tweet by @NthDegree256, I've seen repeated comments that the skill challenges don't have clear failure results. For instance, Skywalker said, "The module as written doesn't give full details as to what a failed result entails."
(Then gives some good suggestions.) I thought I'd cover some of these challenges and give suggestions. (The Keep Hidden challenge already includes failure conditions.)

So MASSIVE SPOILERS AHEAD.

Sneak into Gorizbadd
If the PCs fail to enter the town by one of these options, they still have two other possible paths. Let them revise their strategy and try another way to enter the city. This is extra, and you probably shouldn't assign XP since they failed already. Consider making the second attempt require fewer checks, just so you don't spend too long in the challenge. Alternatively, if the PCs attempted to enter the kobold slums or the forest, they could enter the city at a location they didn't intend to (possibly after being swept down the river or getting lost). This could lead to a combat encounter or a tiring slog through mud or underbrush (causing them to lose healing surges or other resources).

Claim the Stone
If negotiations with Tyristys fail, the dragon commands the PCs to leave. Now, the dragon is still there. The stone is still there. Give your players some time to come up with a crazy plan to get it. I'll just cover a few eventualities:

• The dragon tells the PCs to prove themselves. If the PCs didn't totally bomb the challenge, the dragon might ask them to do something for her in return for the stone. This works especially well if the PCs didn't do much in Gorizbadd before heading to see Tyristys. Give the PCs a quest, possibly one that incorporates one of the setpiece encounters of the adventure that they might not normally see otherwise.
  
• The PCs wait until the dragon leaves to eat, then steal the slaying stone. Even though the dragon didn't care too much about the stone, she still has a dragon's pride. Anyone who steals from her invites her wrath, and she tears the town apart looking for the adventurers. Maybe the PCs need to escape or hide during an intense skill challenge chase. Or perhaps Tyristys just bides her time and causes trouble for the PCs later in their adventures.
• The PCs bribe the dragon. What diplomacy can't solve, gold might. If the PCs try to offer gold and loot, you should let it be successful only if the amount they're giving really hurts. They should be at a disadvantage later. You might have to give them away to make up their lost loot, but make them work for it.
  
• The orcs make a better offer. Since the PCs aren't the only ones after the stone, the orcs might go to talk to the dragon after the PCs' talks break down. The orcs might get the stone despite their obvious unworthiness. Perhaps Vohx offers up one of his underlings as a sacrifice to the dragon. If the orcs get the stone, it's time to fight it out. The orcs won't use it, or all the work they've done to get the damn thing and get paid will be wasted. Though they love to fight, an orc will run away with the stone if the Severed Eyes look like they're going to lose and die.
  

Keep in mind that this challenge has two parts. If the dragon thinks the PCs are trustworthy, but inept, she might behave differently than if she thinks they'll betray her.