Playing zero mana creatures, or having abilities that reduce creature costs on your board to zero, is a quick way to turn Glimpse of Nature from being good to busted
Invasion of Segovia is a perfect example: It creates Kraken tokens, so its already synergistic, and it makes fodder for Jalira, but its not a creature card, so this otherwise subpar hit wont ever be the card you find with Jaliras polymorph ability
These include Gold Stars (Gen 3), Primes (HGSS Era), Prism Stars (Gen 7), Radiants (Gen 8), and now the return of a generation 5 gimmick - Ace Specs which have been given their own rarity
There is a downside to these, of course, as they each cost four energy and lose two energy per attack
A 6 would be 80/20 or better on the front and 90/10 or better on the reverse