Says "prevent damage from a source of your choice" is that a player or like a certain card types instant sorcery creatures enchantments or just damage being dealt from one specific card?
One specific card I think
That's what I thought
{Pay No Heed} put curly brackets. Also just wait Keyoto or somebody will know
Any source that is doing damage can be prevented, instant, sorcery, creature, planeswalker. Whether its an ability or a spell.
119.7. (http://imtgapp.com/forum/index.php?action=imtg;area=rule;number=119.7.): The source of damage is the object that dealt it. If an effect requires a player to choose a source of damage, he or she may choose a permanent; a spell on the stack (including a permanent spell); any object referred to by an object on the stack, by a prevention or replacement effect that's waiting to apply, or by a delayed triggered ability that's waiting to trigger (even if that object is no longer in the zone it used to be in); or, in certain casual variant games, a face-up card in the command zone. A source doesn't need to be capable of dealing damage to be a legal choice. See rule 609.7, "Sources of Damage."
609.7. (http://imtgapp.com/forum/index.php?action=imtg;area=rule;number=609.7.): Some effects apply to damage from a source -- for example, "The next time a red source of your choice would deal damage to you this turn, prevent that damage."
That pretty much somes it up. A player is not a possible damage source in any effect I have seen, it's always spells, permanents, or other effects like an ETB or delayed trigger. The card basically reads as one instance of damage is prevented (combat damage is dealt all at once but is seperate instances for each creature).