Daig, Generous Collector

At the beginning of each player's pre-combat
main phase, that player draws a card and then
exiles a card from their hand. That player adds
{c} to their mana equal to the converted mana
cost of the exiled card.
You may cast spells your opponents own exiled
by Daig, Generous Collector, and spend mana as
though it was mana of any type to cast those
spells.