Maybe it was too early to tell, but having prowess or power matters if they want to keep it in gruul would be the decision I would have made
This leaves us with the outstanding issue of what creature to win with besides Glistener Elf and Inkmoth Nexus
It's worth noting that, when you put the three lore counters on copies you make with Esper Terra's first three chapters, you'll also trigger the first three chapters all at the same time
On the flip side, since your deck is so heavily creatures, that means you have fewer noncreature cards than normal and potentially less resilience to effects like board sweepers
You get incredible board control, a card that works both as a unique combo piece and a payoff for anything generating infinite mana, plus a fantastic mana sink in the hand or on the board
When Death-Rattle Oni enters the battlefield, destroy all other creatures that were dealt damage this turn