I have no recollection of how that happenedI guess I was good at ripping other kids off, and maybe I traded some sports cards for them as well
Now that we have more information, however, it appears things go even further than that
Despite its complexity, regeneration maintained its popularity for many years
The colors are solid enough that you can't see the card through the back of the sleeve, which is a good thing
This is simply an initial try-everything list, but it should quickly become clear what cards do and dont perform in these shells
In summary: Whatever the source (rule or explicit), Breeding Pool needs 2 mana abilities because other cards can take away one basic land type (and thus mana ability) while leaving the other intact - 305.6 simplifies the templating necessary to add and especially take away mana abilities based on the basic land types a land gains or loses