Why is a Lord of Void so dangerous? also what would their personality be like?

Hard to tell about their Personality just like that. Issue with the Lord of Void is the sheer range of powers Void awards, and the immense power behind the Command action of a Lord. Commanding Void, first of all, means the Horrorterrors would definitely do the Lord of Void’s bidding. Then you have the meaning of Irrelevance, and Nonexistance- Both things the Lord would Command, choosing and dictating what is actually Relevant and what doesn’t Exist, this power would pretty much allow the Lord of Void to erase someone’s existence entirely just by willing it. Lies, Misinformation and Obscurity, the Lord of Void would also likely be able to obfuscate any kind of information they don’t want to become public or well known. It’s a fearsome Classpect combo.