Clunkmaster Exclusive
Reduce effects by 1
+3 
Rationale : It'd be nice to have a charm for some of those niche cards that have negative effects but are lower on the number scale to have another charm option other than durian (which you might want to commit onto other cards).
Non Clunkmaster companions tend to not have negative effects related to number effect values other than Bombom which is why the charm is exclusively Clunkmaster. Jumbo has a negative effect but it is attached to their attack rather than effect. Clunkmasters could benefit from this charm though by reducing the deck bricking done by Folby or Scaven (if you're just picking them up as stat sticks), having a Mega Mimik that you actually want, a Plinker that can be a hard carry without an extra crown + card taken up by frostbite shard (or constant inking), and Tootordian that goes off but can stick around!
While durian is a great option for cards like Plinker that dont want their effect at all, there are many cards that have amazing effects with a downside that get removed of their original card identity if they completely lose their effects. Tootordian and Mega Mimik are the examples that come to mind (especially Mega Mimik because it literally cannot attack anymore). For the trash companions if you need a great stat stick early game but don't want to be bricked late game without inking yourself this is also a great alternative. Of course this could also just be a great way to get a funny card if you happened to want to go something like a stacked B.I.N.K while still maintaining it's 'hits all enemies' status.
Why not just crown frostbite shard instead of making this charm?
Crowns are valuable resources that are oftentimes preferably used on companions or count down clunkers instead of spells. This charm gives a gateway into using aforementioned cards without crowning frostbite shard over another card.