Can you put Ivory Mask on a Planeswalker

[Ligom]

Can I put the Ivory Mask on my Planeswalker?

[Void Elemental]

No. You can't put it on anything but the battlefield. It's not an aura.

[Arix]

Note, however, that simply playing Ivory Mask accomplishes much the same thing. If you want to Lightning Bolt a planeswalker, for example, you target the planeswalker's controller with the Bolt, then redirect the damage to the planeswalker. If you have shroud, you can't be targeted by the Bolt, therefore your planeswalker is protected.

It won't stop the planeswalker from being hit with something like Dreadbore, but it's something.