Significance: Blackwall seeks justice and atonement for his own wrong doings, the wrong doings of others, and for those who have been wronged.
Note: The Dragon Age Inquisition Tarot deck follows the Rider-Waite order of cards, which is most commonly used, but this allows us to see and compare some of the nuances that are brought to this card.
The card itself represents: Balance, objectivity, fairness, truth, virtue and honour, dignity and morality, law, etiquette, conscience, equity, reward, advice, equilibrium, someone working on your behalf, verdicts, retribution, natural law, justice, etc.
Blackwall talks to us about what’s right, what’s moral, which is why he later turns himself in, in the end, because he does the moral thing, what is just.
Reversed: Severity, neutrality, bias, misinterpretation, intolerance, gossip, legal actions that are delayed, the fixation for certain things, manipulation, false accusations, imbalance, mental disorder, cloudy perceptions, etc.
He stands stoicly, holding a shield that bears white markings of a sword with rays extending out, a circle within a dotted pentagram, beholding the outreach of elemental energy, more prominently water, depicted by several upside down triangles, symbolising a downward flow, down towards the earth, the earth where one is rooted. He stands his ground as light shines behind him, he shed light on truth and justice will be made.
What I think this means for Blackwall: If justice was fair, Blackwall will stand and fight for what is right.
What I think this means for DA: He may be used as an example to implement justice in the future, perhaps by his own doing, to help people atone for their own mistakes, and becomes a judge of sorts, a reason and justification we may need in future games for certain choices. It could also be used on the flip side of things, where Blackwall is made an example of and people will remember and be told not to pull a Blackwall.
Links to the Tarot Decks Used in the Comparison, the DAI Tarot Deck, and the Books used to determine what the cards actually represent: