Wandertale Mentor
Most fixing creatures are built to be forgotten the moment they've done their job, tapping for a color and fading into the board. The expend mechanic reframes that entirely: push far enough through a turn's mana and a counter lands, which means the very tempo this creature rides along with is what feeds its own growth. The reward loop is self-sustaining without being a combo. Cast enough spells and empty enough of your hand, and a mana dork quietly turns into a real threat. The elegant part is that expend measures your whole turn, not any one trigger, so there is no single spell to hold up or protect and no line to interrupt: the counter is a running tally of how hard you pushed. That also means the counter and the mana it produces are not the same resource fighting each other. This is a creature that wants to sit back early, then start tapping and threatening once summoning sickness has worn off and the curve gets busy, the counter accruing on exactly the turns you were already trying to churn through spells anyway. It is a rate card that gets better the harder you push, and the payoff scales with the aggressive, spell-dense pattern a two-color midrange deck already wants to play. The Bard's job here is to make being greedy with your mana feel like it was the plan all along.
