Learn Finnish: Pimeä tunneli, josta pelastimme ryömijän, loppuu jyrkänteeseen. - The dark tunnel from which we rescued the crawler ends at a cliff.

In everyday speech, you will often hear mistä used for locations. However, standard written Finnish is strict: when referring to a specific physical location like tunneli, you must use the inner local cases of the relative pronoun joka. Therefore, josta (from which) is required here instead of a form of mikä.

Why is jyrkänteeseen in the illative (into) case when the translation says ends "at" a cliff?

In Finnish, the verb loppua (to end) typically requires the illative case. While English describes ending "at" a location, Finnish visualizes the action extending all the way "into" the stopping point.

Where does the word ryömijän come from?

It is the object form of ryömijä (crawler). This noun is built from the verb ryömiä (to crawl) plus the agent suffix -jä, which makes it a "doer" of the action. It gets the -n ending here because it is the total object of the affirmative action pelastimme.

What is the dictionary form of jyrkänteeseen, and why does it look so different?

The dictionary form is jyrkänne (cliff). Nouns ending in -nne change their stem to -ntee- when adding most case endings. To make the illative case, the -seen ending is added to this lengthened stem.