Jade Seedstones // Jadeheart Attendant

In some unusual cases, multiple cards may be exiled to craft Jadeheart Attendant. For example, if an effect makes Jade Seedstones a copy of a permanent with a craft ability that requires multiple components, the copy effect will expire as Jade Seedstones leaves the battlefield and it will return as Jadeheart Attendant. The enters-the-battlefield ability will count all the exiled cards, and you'll gain life equal to their total mana values.

If some of the creatures are illegal targets as the first ability of Jade Seedstones tries to resolve, the original distribution of counters still applies and the counters that would have been put on the illegal targets are lost. They won't be put instead on a legal target.

If a card that isn't a transforming double-faced card becomes a copy of a card with craft, it'll stay in exile if you activate the craft ability. It won't return to the battlefield.

You may exile tokens you control as part of the materials required. However, because they aren't cards and won't stay in exile, any abilities that refer to what you "used to craft" the back faces won't refer to anything.