Thanks! I actually found out something interesting about the Dimensional Rift Gyrados: its signature move, Dimensional Thrash, isn't any type that's in the official games. Jan must have hacked in a new, neutral type to make sure you couldn't cheese the fight with type resistances. Anyway...
Update #6: A Toxic Environment
It's weird: the fight that was supposed to give me Hell was the easiest one for me thus far, and the fights that were supposed to be easy gave me Hell. Venam was no exception, mostly because of that freaking Haunter. Seriously, that thing was a run-ender. Anyway, on TEH URN, I led with Mew, and she led with her Trubbish. Mew set up a reflect type, turning it into a poison-type and giving it a better type match-up, then began spamming mega punch while the Trubbish spammed pound, payback, and Venam's kiss. After it got healed by Venam with all three of her potions, Mew tried using metronome, which turned into rapid spin, of all things. Luckily, Mew was able to take it down the next turn with a mega punch, although xe did get caught in the aftermath. Up next came Venam's Stunky. I healed Mew with a Chinese food, but then got promptly locked into a torment. Luckily, Mew was able to set up an encore thanks to metronome, forcing Venam to switch out to her Tentacool. Mew then landed a mighty mega punch and a fire spin (through metronome, of course) and although xe missed a mega punch and got hit by a water pulse and a fell stinger, xe managed to KO Mew with a metronome-turned aeroblast (because there is no kill like overkill). Up next came the Stunky, and Mew tanked a flame burst to do massive damage with a mega punch. Mew then conjured up a king's shield with a metronome, and blocked a Venam's kiss with it. Mew missed a mega punch and got hit with two flame bursts afterwards, but lived and fired off a metronome-turned-dual-chop and a mega punch, taking out Stunky! Up next came Venam's most difficult Pokemon for me to deal with: her Haunter. I had Mew transform into it, and xe just barely survived a shadow claw to confuse it with a confuse ray. Mercifully, the Haunter injured itself, giving me time to heal Mew with a soda pop while Haunter continued to hurt itself. Mew then finished off Haunter with a shadow claw, but sadly got overleveled, meaning the rest of the fight would be a struggle to keep xem obeying me. After getting smacked by two venoshocks, Mew finally began to obey me and fired off a Venam's kiss while dodging a leech seed. Xe then confused Ivysaur with a confuse ray, causing it to injure itself from confusion twice while Mew got off another Venam's kiss. Sadly, Mew then began to disobey me again, loafing around while getting smacked silly by razor leaves, venoshocks, and Venam's kisses. After I healed xem with a soda pop and xe tanked a razor leaf, xe finally began to obey me again and fired off a mighty venam's kiss, taking Ivysaur down! All that remained was Venam's ace: Seviper. Mew managed to land a confuse ray, and while Seviper injured itself twice, Mew... just kind of loafed around. (sigh) Luckily, while Seviper snapped out of confusion and got off two Venam's kisses, Mew managed to obey me long enough to get off a confuse ray and a critical-hit shadow claw, allowing Mew to tank a few more Venam's kisses and get off another shadow claw, weakening Seviper enough for it to KO itself from confusion damage! With that done, we recruit our first new team member: Venam's Seviper! Now to get the TM for rock smash!
The team so far: