2019-06-14 : Because devour applies as Feaster of Fools enters the battlefield, it can’t devour creatures that enter the battlefield at the same time as it. It can devour creatures that convoked it, and those creatures can reflect upon the wisdom of convoking a demon.

2021-03-19 : If a creature you control has a mana ability with {T} in the cost, activating that ability while casting a spell with convoke will result in the creature being tapped before you pay the spell’s costs. You won’t be able to tap it again for convoke. Similarly, if you sacrifice a creature to activate a mana ability while casting a spell with convoke, that creature won’t be on the battlefield when you pay the spell’s costs, so you won’t be able to tap it for convoke.

2021-03-19 : When calculating a spell’s total cost, include any alternative costs, additional costs, or anything else that increases or reduces the cost to cast the spell. Convoke applies after the total cost is calculated. Convoke doesn’t change a spell’s mana cost or mana value.

2021-03-19 : You can tap any untapped creature you control to convoke a spell, even one you haven’t controlled continuously since the beginning of your most recent turn.