Etali, Primal Sickness doesn't have to still be on the battlefield when someone (preferably an opponent) gets their tenth poison counter
Sanji Blue Character P-095 4 Cost / 4000 Power (Strike) Counter +2000 Straw Hat Crew [When Opponent Attacks] [Once Per Turn] You may trash 1 event card from your hand: Give your leader or up to 1 of your characters +2000 power for this battle
The one thing Historic Merfolk is missing at this point is something like Spreading Seas to give the opponent an Island to power up Master of the Pearl Trident's islandwalk ability
The Mechanist, Aerial Artisan Tacking Clues onto every noncreature spell you cast makes The Mechanist, Aerial Artisan some of the most consistent Clue production we've ever seen in the command zone, and mono-blue has the tools to break it
Trade Stamina naturally restores over time (24 hours for each block) or can be increased using Trade Hourglasses, which can be earned via in-game missions
But when you face a dragon, you don't just keep swinging with the broadsword, do you