The normal pronunciation is /lɪtʃ/ "litch". But the word is very uncommon, which explains why even native speakers might be uncertain about its pronunciation (just as a number of native speakers only learn the standard pronunciation of words like "albeit" later in their lives, if ever). Who can know why the voice actors in some game like Divinity: Original Sin use some different pronunciation like "lick". There are lots of possible reasons:
Maybe they thought it sounded better
Maybe they mistakenly thought it was a German word, like the name "Bach" (which in English is often pronounced with /k/). In fact, the cognate German word is spelled Leich and pronounced [laɪç]
Maybe they had heard this pronunciation from somebody else and just picked it up without thinking about it
In the Wikipedia talk page for the article "Lich", I found one person arguing that "there is plenty of anecdotal evidence that some gamers pronounce the word" as like. I wouldn't attach too much importance to that, though, as there are a number of mispronunciations that may arise in an activity where people mainly encounter unfamiliar words and names in print rather than in speech (see this forum discussion thread: "Okay, that does it. Pronouncing "LICH.") Sometimes a "mispronounciation" becomes so well established that it comes to be accepted as a standard pronunciation of a word (for example, "Wicca" is pronounced /ˈwɪkə/ even though it comes from the Old English word wicca, which is thought to have been pronounced with palatal rather than velar cc, i.e. /ttʃ/). But this doesn't seem to have happened (yet) with /k/-pronunciations of lich: as far as I know, no dictionary records any pronunciation other than the one in -ɪtʃ.
The Wikipedia talk page participant also brings up some information about the etymology of lich and historical variant forms that I think is irrelevant to the way it is pronounced by modern speakers of standard English, but I guess I'll mention it anyway for completeness. The OED says
The Old English líc became by normal development lich(e in the south and like in the north; hence the diversity of forms above. Compare ditch, dike.
