Irregularities can be detected, particularly in the set symbol and in lines that arent straight (see Print Quality and Straight Lines)
These Oil counters do different things depending on the card, but if youre in those colors, you should be looking to spread Oil counters to as many of your cards as possible to maximise the effect they have on the game
Perhaps the one Ive seen the most and has been sent to me the most was the one I thought of first: Jumbo Cactuar, Swords to Plowshares, Aetherflux Reservoir
If youre dying to spread chaos and generally make your competitors have a miserable experience with Lorcana, then emerald cards are the way to go
Trample, lifelink, +1/+1, and a way to threaten the permanents your opponent thought were safe, all on a 1-mana artifact