Martyr's Soul

Both abilities point at the same board state, and that coherence is the design worth studying. Convoke lets a developed team pay for the spirit by tapping down, and the counters reward the very setup that made convoke cheap: cast this without touching a single land and it arrives as a 5/4 instead of a 3/2. The condition is subtler than it looks. "No tapped lands" does not force convoke to cover the whole bill; you can pay with any nonland mana source (a mana rock, a mana dork's own mana ability, a ritual) so long as every land stays untapped. The clean line is to convoke by tapping creatures or spend nonland mana, leave your lands standing, and land the 5/4 with a trick's worth of mana still open. What reads as a restriction is really a tempo filter: the payoff scales with a board you have already committed, and it withholds the counters precisely in the game state where you are scraping for bodies and forced to hard-cast a three-drop off your manabase, tapping lands to do it. The card punishes only the awkward deployment, and that deployment is one you would rather not be making anyway. It is a white aggro reward built for the player already ahead on the board, sharpening a lead rather than rescuing a stalled one.