Sivitri, Dragon Master
The plus ability is the tell that this is a defensive commander built to buy time, not a beatdown engine: taxing every attacker two life apiece keeps loyalty climbing while a slow tribal deck assembles its board. The middle ability is why the card exists at all. A repeatable, unconditional tutor for any Dragon at four mana in the command zone is a rate no other Dragon-tribal legend offers so directly; where a Dragon commander usually wants you to already have the fatties in hand, Sivitri wants to fetch them one at a time, turning a top-heavy deck's worst problem (drawing lands when you needed the bomb) into a non-issue. The ultimate then rewards the whole plan by wiping every creature that is not a Dragon, a one-sided board sweep for a deck built entirely around the tribe. The three abilities lock together with unusual coherence: the plus protects the tutor, the tutor feeds the board, the board survives the sweep. That is the design discipline here. Sivitri does not do anything explosive on any single turn, so the value comes from surviving long enough to grind out card advantage that no opponent's answer can keep pace with. As a mono-purpose commander, she is narrower than most planeswalkers legal for the role, but the narrowness is the point: a Dragon deck's leader that does Dragon things and only Dragon things, well.
