So I wanted to try my hand at creating some custom cards for my cube, mostly because I kinda want to have a few more half decent threshold creatures in red, and I'm not happy with the 1 and 2 cmc slots, but I have no idea what I'm doing so I could use some help.
I'm considering something like this to replace
Illustrious Historian, because creating a permanent token doesn't really feel like something red should be doing. Incidentally, 3 damage just about nukes everything in my cube, creaturewise, and it could work as a bolt to the face for aggro decks. Not sure about the cost for the bolt yet, though. 1 mana and Threshold is probably fine, since it's what you pay for
Fiery Temper's madness cost.
or
I would like a red one drop with threshold, but I don't want it to always flat out overpower
Nimble Mongoose. Having 1 toughness after threshold hits still makes it very vulnerable to removal while Nimble Mongoose with its 3 toughness and shroud tends to stick around. I'm torn between giving it first strike or flanking, and I'm not 100% sure about the power increase/menace.
I have flanking as a keyword in Boros (yes, the powerlevel is that low), so having a 1 drop would fit and would likely also encourage more aggressive play patterns. There are a lot of 1 toughness creatures in my cube, so a first striker or flanker is usually annoying to block, even if it has just 1 power.