You can use activated abilities whenever you have priority and can pay the cost
Image via Wizards of the Coast LLC Nissa, Ascended Animist A new Nissa planeswalker is a real treat for mono green stompy decks with Awaken the Woods, as you can use Dryad lands to ramp into her ultimate ability and give them a powerful boost, as all these lands are also forests
Your opponent needs an obscene amount of pressure just to keep up with that
Thankfully, targeted removal on the transformation into Hydaelyn, the Mothercrystal makes the card draw even better with upside, assuming you're able to keep another legendary creature around
That'll backfire on legendary creatures, unless of course, they have a relevant enter-the-battlefield trigger
Kronk - Head of Security has a very high summoning cost of 7 Ink, but he has Strength and Willpower stats of 6 each