Jamie McCrimmon

The +X/+X trigger looks modest until you tally what qualifies: every legendary spell, every artifact, every Saga counts as historic, and the buff scales to the exact mana value of whatever you cast. A two-drop legend adds two, a six-mana artifact adds six, and trample carries the surplus through whatever tries to block. That turns a plain 2/2 into a running measure of the deck's own top end, spiking hardest on the turns you were already deploying your expensive threats. The Doctor's companion clause is the structural payoff. Pairing him with a Doctor lets both sit in the command zone, and a Doctor deck is a legendary-spell deck by construction, so the historic count is not a build-around tax so much as a natural consequence of the pairing itself. Most companion designs lean on the Doctor for the engine and leave the companion as flavor; here the companion is the piece converting the deck's density of legends and artifacts into combat math. The whole design lives in the seam between the counting clause and the pairing rule. On his own he is a beater that grows when you spend, and the buff is temporary, so he wants you casting in his combat turn rather than banking value. Harnessed to a Doctor, he becomes the reason a legendary-heavy list develops the board instead of hiding behind it.