As for Runehorn Hellkite, I've never met a Wheel of Fortune I didn't like, and even though this one is pretty expensive at six mana, it also generates random value from the graveyard if you discard it to something like Survival of the Fittest and is uncounterable and instant speed
You can also take advantage of both individual and mass blinks, like Felidar Guardian and Laezels Acrobatics to not only get more Cat per cat, but also protect Arahbo should he get targeted
The hype surrounding this Planeswalker is through the roof, and for good reason
Bringing multiple copies of this card into play over the course of several turns could really slow down the opposition
You should pair it with haste enablers to mitigate the chance of this green creature dying before it exerts a creature into play
That means no Sram, Senior Artificer in an Equipment deck and no Simic Growth Chamber in a blue-green deck