Thanks to the rounded down wording, your opponent is always left with at least one creature, so they can always keep their best creature alive
Grist, the Hunger Tide: A planeswalker you can nab with Collected Company
You only play it when you want the reusable graveyard but the life gain is what makes it playable
Prophet of Kruphix has a similar untap ability, but when combined with the Prophets You may cast creature spells as though they had flash ability, the card was too good and was banned from Commander
Thats a powerful and scary ability in Gruul, and itll end up playing out similar to the new Ghalta, which I am terrified of and slaps people around basically every time it resolves
It also has a triggered ability that creates a tapped 1/1 flier whenever a spirit you control phases back in