ef707e6d5d
usage tap lands to produce mana then sacrifice an offering... example
you have Guttersnipe in play, it has a mana cost of {2}{R}, and you have
Patron of the Akki in hand that costs {4}{R}{R}. You need to produce
{2}{R} mana first before casting Patron of the Akki, then choose
Guttersnipe as an offering.