The supporters Pass is a special Game Pass that's suppose to be a channel for those who wish to contribute to the R2D Development.
|Type of Pass||Donation|
"Special pass for those who support R2D by generously donating 1,000 R$ to the continued development of R2D. This pass unlocks the secret mob: Duck." -Gamepass Description
The supporters pass was added in v35 as a way for people to support the R2D Development without having to buy none needed credits. To be fair, the Duck was unlocked when purchasing this item thus all ducks aught to be highly appriciated as they keeps the game going.