Well, I think the best way that you can answer this question is to actually read the story yourself and come up with your own adjectives to describe the impressions that you had, because this is a rather general and broad question. However, just to get you started and maybe to give you some ideas, here are my suggestions.
Firstly, I would describe this story as suspenseful. The way in which the setting is introduced with the feud between the two families and the storm during the night strongly suggests that something violent is going to happen during the course of the story.
The second adjective I would use to describe this story would be heartwarming. The way in which the tragedy that befalls both Georg and Ulrich forces them to confront each other and become reconciled to each other is something that gives us hope that even the worst forms of emnity can be healed.
Finally, the ending of the story causes me to describe this story as despairing. The way in which the men are not found by other men who will help them but by wolves who will only kill them makes this story despairing in terms of the way it presents the fate of these two men.
One adjective that can certainly be applied to Saki's short story "The Interlopers" is ironic. In Saki's story, two antagonists who would gladly preside over each other's deaths arrive at a state of grace. Trapped by a fallen tree, they reconcile their differences and develop a cordiality toward each other that, had the story's ending not suggested a horrific death at the mouths of a pack of wolves, would seemingly lead to friendship. The story is ironic, however, because these two enemies-turned-friends manage to put aside their mutual antipathy only to realize they are about to be eaten by the aforementioned wolves.
Another adjective that applies to "The Interlopers" is suspenseful. Saki injected considerable suspense into his narrative as the two characters, Ulrich and Georg, converge in the forest in a scenario that could lead to the violent escalation of a generations-long feud between their respective families. The suspense exists by virtue of their encounter in the woods, both men armed and prepared to kill the other. Note, in the following passage, how the author builds suspense:
The two enemies stood glaring at one another for a long silent moment. Each had a rifle in his hand, each had hate in his heart and murder uppermost in his mind.
Saki continues to build suspense with the falling of the tree onto both men, leaving them pinned to the ground and dependent upon rescue from others. Finally, he uses suspense to end his story. The two men have, as noted, reconciled their differences and are developing a common bond. Then, in the story's final sentence, Ulrich informs Georg that the noises that the latter assumes belong to a rescue party are actually caused by the approaching wolves. The story ends with the presumption of a horrible death.
A third adjective that can be applied to "The Interlopers" is hopeful. As Ulrich and Georg lie trapped together in the woods, and as they discover that the feud that has riven their community for generations has been wasteful and devastating, Saki injects an element of hope into his narrative. The two men resolve to end this senseless feud, and a sense of optimism permeates the atmosphere. As Georg hopefully suggests,
How the whole region would stare and gabble if we rode into the market-square together. No one living can remember seeing a Znaeym and a von Gradwitz talking to one another in friendship. And what peace there would be among the forester folk if we ended our feud to-night.
Saki gives the reader a false sense of security. He takes these two antagonists and enables them to put aside their grievances and murderous intentions. There is hope, at least for a while.