Quirion Sentinel
{1}{G}
Creature — Elf Druid
Oracle Text
When this creature enters, add one mana of any color.
Watch Out
ETB trigger, not a cast triggerRules Note
This card's ability triggers when it enters the battlefield, not when it's cast. Effects that double ETB triggers (like Panharmonicon) work here. Countering the spell prevents the creature from entering, so the ETB won't fire.
Mana abilities don't use the stackRules Note
If this card's activated ability produces mana and doesn't target, it's a mana ability. Mana abilities resolve immediately without using the stack — opponents can't respond to them. However, abilities that target (even if they produce mana) aren't mana abilities.