Nullhide Ferox

Hexproof
You can't cast noncreature spells.
{2}: This creature loses all abilities until end of turn. Any player may activate this ability.
If a spell or ability an opponent controls causes you to discard this card, put it onto the battlefield instead of putting it into your graveyard.

The List

Guilds of Ravnica

Hexproof
You can't cast noncreature spells.
{2}: Nullhide Ferox loses all abilities until end of turn. Any player may activate this ability.
If a spell or ability an opponent controls causes you to discard Nullhide Ferox, put it onto the battlefield instead of putting it into your graveyard.

Nullhide Ferox's activated ability can be activated only while it's on the battlefield. Players can't, for example, activate it to try to stop its replacement effect from putting it onto the battlefield.

Once Nullhide Ferox has lost its activated ability that makes it lose its abilities, that ability can't be activated again until the turn's over.

Once Nullhide Ferox's activated ability has resolved, it can gain new abilities. It won't lose those abilities.