Why you should NOT build: At the end of the day, when you have a format that is insanely reliant on evolving almost all your Pokemon, setup is going to be the only thing that really matters
There are other benefits to these spells that make them slightly better than a 1-for-1 exchange, but they do not put you up on cards or any sort of permanents in play, and are therefore not card advantage
If the spell has any mandatory additional costs, those must be paid to cast the spell
If the rest of the bonus sheet is like this, it will provide needed reprints without unbalancing draft and sealed games with extra bomb rares
Rubinia Soulsinger was among the reprints of Commander 2013, and Sheppard updated the character to be featured with a scroll and quill, holding the items temptingly toward the viewer, almost as if shes asking for the viewer to sign their soul away