Cerbor, God of shields

Menace, mountainwalk, indestructible. Whenever one or more of your creatures gets +1/+1, put a +1/+1 counter on cerbor.
When cerbor, God of shields, enter the battlefield, put two +1/+1 counter on. each of your creatures. When cerbor attack, put a +1/+1 counter on target creature.
{t}: counter target instant