Virtue of Loyalty // Ardenvale Fealty
The end-step trigger is what makes this an engine rather than an anthem: a static +1/+1 boost would size your board once, but putting a counter on each creature you control every turn compounds, and untapping them means a go-wide team can commit to an alpha strike and still stand back up to block. The counters also change what survives. A sweeper keyed to toughness can whiff on a board that has been growing for several turns, and once the counters are on your creatures, removing the enchantment that granted them leaves those gains untouched, unlike an anthem effect. Committing five mana to a single enchantment all at once is a real cost, though, which is where the split earns its keep. Ardenvale Fealty for buys a vigilant Knight token that holds ground while you develop, and the enchantment waits in exile until you can afford to turn the corner. That Knight is still on the battlefield collecting counters once Virtue of Loyalty comes online, so you get value out of the card on an early turn and never surrender a blank one. And because the trigger fires at your end step, the growth can begin the same turn it lands as long as it resolves before that step, then compounds from there.
