I am a little confused on the terms hit vs damage. Harpoon for instance is set of by a critical hit, show you the dark side is set of by a critical damage. So they are different?

In the case of Harpoon vs ISYTDS, the difference is that Harpoon requires there to be, at the Compare Results Step, at least 1 critical result that is uncancelled. In the case of ISYTDS, it is triggered by an uncancelled crit that then progresses into Step 7 on the Attack Timing Chart, where the damage is actually dealt.

An interesting example is Lt. Blount, who always has his attack hit, even if any hit/crit results he rolls are canceled out. That allows him to trigger the abilities of cards that have 'when you hit' printed on them.

9 minutes ago, librarian101 said:

I am a little confused on the terms hit vs damage. Harpoon for instance is set of by a critical hit, show you the dark side is set of by a critical damage. So they are different?

Yes, they're different. They seem similar because they're both related to a crit, but the triggers are different.

Harpooned! does something extra if you're hit by an attack when there was an uncancelled crit, to my understanding at Step 6.iv in the Attack Flowchart on Page 8 of the FAQ.

I'll Show You The Dark Side, roughly speaking, replaces the effect of a critical damage suffered while defending with it's particular crit, and happens at step 7.ii or 7.iv (it can happen in either, depending on the number of shields on the defender and the number of hits in the attack) on the Flowchart. The normal effect of the crit is to either [1] remove a shield [2] deal a face-up damage card. ISYTDS instead deals the assigned card, whether or not there are shields.

Thanks