Fissure and Horn Drill are egg moves for Lapras in Sword and Shield. The move reminder cannot teach Lapras these moves.
So one must do the following:
First, delete two moves from Lapras’ moveslot.
Second, one needs to acquire another Lapras (preferably from the VC first gen games, so that it can learn Horn Drill via TM) that knows Fissure and Horn Drill.
Lastly, one must put both Lapras in the Day-Care and the two-move Lapras will learn Fissure and Horn Drill.
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