Sukhjot needs light in order to sustain itself, and the best source of light are Light type creatures, so it instinctively moves toward concentrated groups of Light types, at which point they get absorbed into its core in a gruesome and painful fashion. It is very possible that it has killed millions of Light types this way; before it was sealed, it brought the Light types to near extinction. It is also capable of mind control, which it used in order to force Rubidus critters to catch Light type