Eerie is a new mechanic introduced with Duskmourn that is a trigger gained every time an enchantment enters the battlefield under your control or you fully unlock a Room you control
In the mainline games, Nickit is not a starter or legendary Pokmon, but it plays an essential role as one of the early-game Pokmon that trainers encounter on their journey
Since Im not really worried about whether Chromium is good enough, my financial questions must do more with how the metagame is likely to develop
So you can potentially see unhealthy combos like that arising again with things like Shiftry (NXD 72/99) from Next Destinies, or Vileplume from Ancient Origins, or Exeggutor (PLF 5/116) from Plasma Freeze, which are all just incredible Grass-type Pokemon that are held back by the fact that they're Stage 1 or Stage 2, which is a good way to cripple a card -- or to balance a card, I should say -- to give it a really strong ability, but you make it a Stage 1 or Stage 2, and it's slower
Its likely the best overall card and worthy of the ban discussion it receives