Artifact Creature - Golem
Platinum Primus is indestructible.
Platinum Primus's power and toughness can't change. (Effects that would increase, decrease, or switch its power or toughness instead don't.)
Just my addition to the "platinum" family (alsongside Platinum Angel and Platinum Emperion). I hope the "indestructible" doesn't feel tacked on - it's just that its other ability isn't really that impressive on its own.
I originally had a clause on it that prevented counters from being put on it (like the one on Melira, Sylvok Outcast) to avoid confusion, but the second ability should take care of that: -1/-1 or +1/+1 counters can be placed on it, they just do nothing. I thought it read more elegantly that way.