Tocasia's Onulet

If a permanent returned to the battlefield with unearth would leave the battlefield for any reason, it's exiled instead—unless the spell or ability that's causing the permanent to leave the battlefield is actually trying to exile it! In that case, it succeeds at exiling it. If that spell or ability later returns the card to the battlefield (as Static Net might, for example), the permanent card will return to the battlefield as a new object with no relation to its previous existence. The unearth effects will no longer apply to it.

At the beginning of the next end step, a permanent returned to the battlefield with unearth is exiled. This is a delayed triggered ability, and it can be countered by effects such as Defabricate that counter triggered abilities. If the ability is countered, the permanent will stay on the battlefield and the delayed triggered ability won't trigger again. However, the replacement effect will still exile the permanent if it eventually leaves the battlefield.

Activating a card's unearth ability isn't the same as casting that card. The unearth ability is put on the stack, but the card is not. Spells and abilities that interact with activated abilities (such as Defabricate's second mode) will interact with unearth, but spells and abilities that interact with spells (such as Scatter Ray) will not.