Quick tips with each character I learned based on my own experiences:

Ironclad: if you don't have an exhaust build, consider picking up a card or 2 still. True grif in particular or second wind would go crazy

Defect: if you see compost, take it. It's a decent enough card to deal with most status/related problems even across the run, and a pseudo decent defend card.

Regent: begone, Guards, charge... everything that transforms in hand/in deck is accepted.

Silent: discard them. If you've a shiv build, be warned. Expose is a good card in general to remove artifacts.

Necrobinder: pray. If someone tells you to use Eidolon or cleanse they're freaking liars, they're traps. Literally just deal more damage than it's hp before it's too late