

Sorry, I dont know what stage of the game you are in so I can't tell you how much accuracy you need for whatever clan boss you are on.

Yes, an accuracy banner will give around 65 accuracy, but you want to be at around 150 for midgame clan boss.

Looking at your stats, his accuracy is too low to land his poisons in most areas of the game, even early level so you definitely need more accuracy for clan boss. If you already have a arena nuker and campaign farmer than build him with defense and accuracy for dungeons and clan boss. If you don't have a campaign farmer or arena nuker and have better poisoners then build him with crit rate and crit damage. Now I am not sure how far you are into the game, but build kael for what you need. Kael can be rather tricky to build in the early game simply because he is so versatile everywhere.
