I didn't have G-Booster, so I used G-Scope as my ACE SPEC (and I still used Cheren in my deck)
Now, with a few Zombies, you can start sacrificing them to Kalitas to put two +1/+1 counters on him, quickly making him a major force to be reckoned with
Chart shows the price of Heracross #18 at the end of each month going back as long as we have tracked the item.

Promotions Fresh Re-Stocks -13% Japanese Pokemon Center - Special Box Collection - Hiroshima Regular price $199.95Regular price $229.95 -13%Sale price $199.95 -16% Japanese Pokemon Center - Special Box Collection - Tohoku Regular price $159.95Regular price $189.95 -16%Sale price $159.95 -18% Japanese Pokemon Center - Special Box Collection - Fukuoka Regular price $179.95Regular price $219.95 -18%Sale price $179.95 Sold out Mega Evolution: Pitch Black Booster Box Regular price $199.95Regular price $219.95 -9%Sale price $199.95 Sold out Mega Evolution: Pitch Black Elite Trainer Box Regular price $77.95Regular price $84.95 -8%Sale price $77.95 -12% Mega Evolution: Chaos Rising Booster Box Regular price $189.95Regular price $214.95 -12%Sale price $189.95 -24% Mega Evolution: Perfect Order Booster Box Regular price $174.95Regular price $229.95 -24%Sale price $174.95 -20% Japanese Mega Dream ex Booster Box Regular price $119.95Regular price $149.95 -20%Sale price $119.95 Japanese Mega Dream ex Booster Pack Regular price $13.49Regular price Sale price $13.49 -24% Japanese Abyss Eye Booster Box Regular price $94.95Regular price $124.95 -24%Sale price $94.95 -13% Japanese Ninja Spinner Booster Box Regular price $104.95Regular price $119.95 -13%Sale price $104.95 -13% Japanese Inferno X Booster Box Regular price $173.95Regular price $199.95 -13%Sale price $173.95 NEW

Crow, Dimensional Fissure, Macro Cosmos, Shadow-Imprisoning Mirror and more can prevent Dark World from setting up, and once that happens at a crucial timing, it completely stops their momentum for upwards of several turns
Or find out how many Pokmon there are right now.