No abilities of creatures your opponents control can be activated, including mana abilities.
14-03-2017
wotc
Linvala’s last ability affects only creatures on the battlefield. Activated abilities that work in other zones (such as bloodrush or unearth) can still be activated. Triggered abilities (starting with “when,” “whenever,” or “at”) are unaffected.
08-06-2016
wotc
Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keywords are activated abilities and will have colons in their reminder text.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.