Thornwall is a legendary major card out of the New mechanic pool. Bulwark's plates reflect 40% of damage taken for a 30% longer window; the slam is 60%.

You can take it once · it only turns up when your Special ability can actually use it · it can be offered for 0 of the 34 abilities.

Only one card can reshape that ability this way — this one, or Rampart Charge and Standing Bulwark. Take one and the rest are gone for the run.