Magikrab is obtainable by remastering an Astral Traffikrab. In order to catch the astral crab, you may need to beat the story and get a ritual candle. You can sacrifice an astral tape and comb the beach area for any fusions with a crab or you can sacrifice a crab and check all fusions to see if one rolls astral. It is best to turn off autosave as running from a fusion will waste your candle. You will need to quit or alt+f4 without saving to reload the game. If no fusions on the map have the crab you are looking for, you will need to sleep to the next day and try again.