LogFAQs > #961731168

Yeah they're cross converters. Basically creates a crapload of their element's tiles in a cross shape, generally a late game necessity because bursting with a big board is almost always better than just converting a few at a time and relying on luck.

Maggie is good, but generally Barton and Sikare are considered more valuable. I'd say you can hedge your bet a bit and just go Sikare so that one day you can get a great base to use Lucoa. Forest is considered the best element with some debatable match ups favoring other elements, so it wouldn't be too hard to get other pieces of the overall team.

Just go for whoever looks good though. You have Eicy and Faust, so you can rely on them in terms of meta and just pull whoever you like more