Imploring your deity’s aid requires you to use your action. Describe the assistance you seek, and roll percentile dice. If you roll a number equal to or lower than your cleric level, your deity intervenes. The DM chooses the nature of the intervention; the effect of any cleric spell or cleric domain spell would be appropriate.
If your deity intervenes, you can’t use this feature again for 7 days. Otherwise, you can use it again after you finish a long rest.
At 20th level, your call for intervention succeeds automatically, no roll required.
That's a cool story. Thanks for sharing. How did the characters survive the 80ft fall?
So on this, the story provided by @Greg Benage above is a perfectly acceptable use of the ability, and one that fits with its intent. The God pulls the cleric out of danger by casting the perfect spell for him. But if your character is expecting Helm to personally show up and start punching a dragon, then they're only going to get that if you, the DM, decide it'd happen.
Yeah, in this case, the cleric (whose deity was indeed Helm!) lacked language and couldn't ask for any specific aid.I just chose a way for Helm to intervene decisively with the least effort possible. So he helped his cleric help himself.
So on this, the story provided by @Greg Benage above is a perfectly acceptable use of the ability, and one that fits with its intent. The God pulls the cleric out of danger by casting the perfect spell for him. But if your character is expecting Helm to personally show up and start punching a dragon, then they're only going to get that if you, the DM, decide it'd happen.
It's D&D and they're 20th level: It's only 8d6 bludgeoning and prone.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.