If this creature gets enough -1/-1 counters put on it to cause it to go to the graveyard, modular will put a number of +1/+1 counters on the target artifact creature equal to the number of +1/+1 counters on this creature before it left the battlefield
(When it dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.) If a card with persist is removed from the graveyard after it dies but before the ability trigger resolves, it won't be returned to the battlefield
This output can be formatted as a checklist, which shows a variety of information about each card
A favorite of goblin players, it can buff your board while doubling your mana
Still, it fits my criteria of being an older rare and has a surprisingly useful effect
Compared to Ewit, that's a difference of roughly 45,000 decks