This third ability comes in handy in several Commander strategies (filtering cards by paying life is usually a very good deal), but of course Mystic Forge is most valuable in colorless or artifact-focused builds
At five mana, its a bit too expensive for my liking, even if it ramps you
You can proliferate these, but it'll only matter if opponents try to remove counters one by one since a death trigger or trip to exile resets counters anyway
Focus on cards where the PSA 10 premium exceeds 3 the raw price plus grading fees
I think Glissa gets into the lower bomb range
In addition, whenever a Nazgl enters the battlefield, they will trigger Tales of Middle-earths new The Ring Tempts You mechanic, as well as adding a +1/+1 counter to any Wraith creatures (which includes the Nazgl) when a player is tempted by the Ring