I bet TrapKnight have plenty of ideas but I guess wont harm to share my own, The worst that can happen is he ignores me :)
1: an insect area when Rena is slowly transformed into an insect by means of smaller ones attaching themselves to her or going inside her, sort of like in a flesh area but it accumulates more slowly, is harder to get rid of, and causes buffs and debuffs on a greater scale,
2: a robot area when at the start Rena is injected with nineties and slowly transforms into a robot in a similar fashion but faster and with more variation