"I feel the vine-rhythm as my friends drive the beast to me. I will not miss my mark."

Drumhunter

At the beginning of your end step, if you control a creature with power 5 or greater, you may draw a card.
{T}: Add {C}.

The List

Starter Commander Decks

Commander 2013

At the beginning of your end step, if you control a creature with power 5 or greater, you may draw a card.{T}: Add {1} to your mana pool.

Shards of Alara

At the end of your turn, if you control a creature with power 5 or greater, you may draw a card.
{T}: Add {1} to your mana pool.

The first ability has an “intervening ‘if’ clause.” That means (1) the ability won’t trigger at all unless you control a creature with power 5 or greater as your end step begins, and (2) the ability will do nothing if you don’t control a creature with power 5 or greater by the time it resolves. (It doesn’t have to be the same creature as the one that allowed the ability to trigger.) Power-boosting effects that last “until end of turn” will still be in effect when this kind of ability triggers and resolves. An ability like this will trigger a maximum of once per turn, no matter how many applicable creatures you control.