The term 'Ruler of Asgard' can be summarized by the crossword solution 'ODIN', which is a four-letter word. ODIN is a major deity in Norse mythology and is the ruler of Asgard, the home of the gods. He is often referred to as the Allfather, as he is the father of many of the other gods. ODIN is associated with wisdom, war, death, and magic, and is also known for his one eye, which he sacrificed in order to gain knowledge.