His card stretches the definition of the "Mystic Arcanum" ability, which usually refers to a warlock spell of 6th level or higher
Lands could now be banned if they had abilities that werent mana abilities, or didnt add counters for later mana production (like storage lands)
Each of these Clue characters is a legendary creature and a mechanically unique card, complementing a slew of other mechanically unique cards mixed into the set
If you are able to cast Deep Water, youve already gotten two blue sources available
Having a bit of blue in the cost will naturally make the card narrower but far less so than with most gold cards simply because of where it is used
I think that this card is great for utility in decks such as Neyith of the Dire Hunt and Grothama, All-Devouring that care about fighting, but I also consider this an amazing top-down design from a flavor perspective