The second benefit does apply more specifically to Planeswalkers, but having loyalty abilities cost +1 loyalty extra is something a lot of unaware players might trip over, thanks to it being framed more like a negative
For Steel, Tiana, Celebrating Princess showcases that if you keep your hand empty, you can actually gain benefits
The combination of both sets you up to do ridiculous things that were not meant to be repeated
5 Karumonix, The Rat King Bring The Infestation One of the more interesting Commanders on this list, Karumonix, the Rat King is a pretty big divergence from other poison-based legendary creatures on this list, but that doesnt make him any less impressive
Any repeatable proliferate effect synergizes well with everything from planeswalkers to poison counters and beyond