Modern keeps the price somewhat high, but it's worth it since you now have the power to cast auras and equipment at flash speed and place equipment on creatures for free on ETB
The main reason I say these arent worth it is that a set pack from the LotR set is about $6
An invisible ink card is a special variant of the regular version, that basically looks the same, but is exclusively foil and has extra in-universe text from the investigative crew taking notes about the character
After that, start trying to get some token generators on the battlefield so you have fresh bodies each turn (or a ton all at once) that can be sacrifice fodder
And once again, Zinnia comes along and lets you have two of these Otter Artificers thanks to the Bird Bard bestowing offspring to all of its loyal listeners
MTG Murders at Karlov Manor story Ravnica, with such wholesome guilds as the killer clowns, vampire bankers, zombie farmers, and sneaky assassins is pretty murdery already