I had the idea for a super rare Guardian card maybe called Benitoite (super rare blue gem) or platinum maybe. Something better than killer that does not need to be recharged however to balance things out maybe only one member of your team can have it at once? Maybe the card comes with a secondary negative effect that is also constant?
Personally, I want corrupted guardians. They have a very good positive effect and a very bad one. Think of a vampire corrupted guardian this way. Vampirism is always activated and an ender isn’t needed to trigger it. However, you always lose health, meter, and instinct over time. Snake can be you always deal to your opponent potential damage but you take some as well.
What about an option to automatically refill Guardians? If you activate it for a particular guardian, each time it goes to 0 charges, it automatically recharges to max charges
Also I do like a lot the “corrupted” guardians, with both good and bad effects.
EVEN MORE: SL mimics, Omen and Gargos could use them, giving our enemies better tools