Can I put this on an enemy character to lower its defense?
[Source: WotC]
No. You can put Upgrades on your characters only.
If I play this on a character with 0 defense, and then later something gives it +1 defense, what will its total defense be?
[Source: WotC]
0. Erratic Lightning won’t drop your character’s defense below 0, but the -1 applies again once your character’s defense is raised.
For Erratic Lightning, does the -1 defense apply to defense flips, or only to base defense? For example, the upgraded character has 0 base defense, and flips 2 blue pips on defense. Does the upgraded character defend for 1 or 2?
[Source: WotC]
It’s the sum of the flips, so you do all of the math first. The character in this scenario would defend for 1.
Power Punch stays on the other character. Erratic Lightning gives Optimus +3 attack.