Auras and Equipment cards have gotten stronger over time, and so has their support
You can also grow a Protean Hydra by removing a counter before each opponents end step, creating a potential monster quickly
Mono-black cards like South Wind Avatar can support these strategies, but its most often used in sacrifice strategies with Blood Artist or Zulaport Cutthroat, or with commanders like Vito, Thorn of the Dusk Rose
I also like this in shells like Discard-Matters combining this with Megrim effects, Reanimation, Midrange that wants card advantage ETB triggers, Blink that wants to have ETB stuff to blink over and over again and +1/+1 Counters-Matter where this is a nice way to add counters onto an ETB body
Poison the Waters Hee-hee
They come in and trigger effects on each turn like a saga, but while they're on the field can also block and attack and behave as normal creatures