Halloween event?

It's empirical observation. I noted that I was having a really tough time with the Rikti in an invasion in Galaxy when I was level 4. I just wasn't taking much of his health per hit. I looked at what my damage was, and saw that it was the same as I was doing to even-con mobs, then I checked his hit points and wrote the number down. I didn't have to look far for what level they were native to, since I had suspected when noting the high number that they were using level 30 hit points, as that is the minimum level that Rikti spawn. Sure enough, a quick look at some level 30 mobs showed the same hit points as invading Rikti have. The bombs and heavies are even worse, at native level 50 hit points. I haven't done a similar measurement for zombies, so I can't tell you what their hit point base is.

Edited to add: It's even simpler than that, really. If you get a recipe from an invasion mob, note the level. That is the native level of that mob.

Yeah, that was a pretty awesome moment.

If I'm playing a toon below say about 15, I don't bother even trying to go after a Rikti Bomb because my damage is so piddly and they regen too quickly. And I love invasion events. :P So I think this whole thing may have some merit.

Speaking of invasion events, the story above about the devs enjoying watching people freak over the first early zombie invasions is pretty cute. ^^

This year with SSK presumably it'll be worth teaming lowbies with highbies as they should do more relative damage.

I could be wrong on this but I think if you hit a bomb thats later destroyed it'll count towards the badge. So pick on bombs that other people are hitting or hit each bomb once and then find another one in the hope someone else destroys it

I think it requires some minimum level of damage for it to count.

Yes and let's hope that they don't launch it at the same time the techs start to breakdown the game room.

Ah, memories...running down the hall after dinner to play and discovering computers being taken apart.

It was still fun to watch over people's shoulders, though.

Yes, I think you need to do 10% of the damage in order to get badge credit. As for XP, I think that is directly related to the percentage of damage you inflict.

Standard defeat badge requirement is that you have to inflict 10% of the total hit points. As part of an invasion, bombs might be different but I can state that doing one small tap then moving on is NOT sufficient. (No, I wasn't trying to leech, but sometimes I get to a bomb late and can only land a single blow before it's destroyed.)

BTW, when I say "you" have to inflict 10%, "you" means the entire team. A player can stand there buffing, debuffing or healing and still get credit. Also, note that the 10% refers to the total hit points inflicted to defeat the enemy - this is why you can defeat Eochai and Jack but not get the badge if they have been smacking each other for a while. If they've done a million points of damage (which was regenned back) and you do 30,000 to defeat one, you have not hit the 10% milestone.