Ovinize doesn’t counter abilities that have already triggered or been activated. In particular, you can’t cast this fast enough to stop a creature’s “At the beginning of your upkeep” or “When this creature enters the battlefield” abilities from triggering, since they trigger before players get priority.

If the affected creature gains an ability after Ovinize resolves, it will keep that ability.

If a face-down creature is affected by Ovinize, it won’t be able to be turned face up for its morph cost. If some other effect turns it face up, it will remain a 0/1 creature with no abilities until the turn ends. Its “When this creature turns face up” or “As this creature turns face up” abilities won’t work.

Ovinize can be used to disable a creature’s vanishing ability permanently by casting it in response to the vanishing upkeep trigger when there’s one time counter left. The last time counter will be removed as that ability resolves, but since the creature no longer has vanishing, the “sacrifice” triggered ability won’t exist. When Ovinize’s effect ends and the creature regains vanishing, its triggered ability will no longer be able to trigger because it has no time counters.

If Ovinize affects Mistform Ultimus, the Ultimus will lose its ability that says “Mistform Ultimus is every creature type,” but it will still *be* all creature types. The way continuous effects work, Mistform Ultimus’s type-changing ability is applied before Ovinize’s ability removes it.

This is the timeshifted version of Humble.

Removes all creature abilities. This includes mana abilities. Animated lands will also lose the ability to tap for mana.