Before you even get to the Save Sphere there's a chest on the left which contains 2 Phoenix Downs. Past the Save Sphere on this side is another chest containing 2 Hi-Potions. Most of the enemies you'll encounter on Thunder Plains are obviously thunder-based, so weapons with Waterstrike will help out a lot. Here's a list:
- Melusines are lizards, so they're quick and agile, and have a higher rate of inflicting petrification and/or silence with their attacks compared to previously encountered lizards. Thankfully, Tidus still finds it easy to hit them, and one hit from him (especially with a weapon with Waterstrike, which the Brotherhood recently gained) will kill them.
- Kusariqqus are armoured dragons, and they have quite a painful physical attack (sometimes doing up to 900 damage, although around 450 usually). One hit from Auron will kill them, though, or two hits from Kimahri.
- Aerouges are flying mages. Their Thundara attack is particularly pathetic for it being an -ara spell, doing at most 300 damage. This is also their only attack, and they're vulnerable to Silence which renders them completely harmless. However, one hit from Wakka's ball kills them so inflicting Silence on them without killing them is difficult. You can Steal Lightning Marbles from these as well, which is better than the Electro Marbles you get from Larvae or Gold Elements.
- Buers are flying eyeballs. These are the same as the ones you encountered before, except they do a bit more damage. Their stare attack still inflicts confusion occasionally, and one hit from Wakka still kills them.
- Gold Elements are beefed-up versions of the Yellow Elements you encountered in Kilika Woods. One Watera from Lulu will kill them, but otherwise they have 1200 HP that is difficult to deplete quickly with physical attacks. They can't use Thundara but their Thunder attack does between 500-600 damage, so watch out (Yuna casting NulShock helps a lot).
- Larvae are new monsters. They have around 1500 HP, and use Thundara a lot for about 400 or so damage. They'll survive one Watera, and can heal themselves with Thundara, as well as bolstering their Magic. Don't let battles with these drag on too long or their Thundara will quickly be doing over 800 damage. One Watera followed up with one hit from Auron will kill them.
- Qactuars are Final Fantasy X's incarnation of an old favourite, the Cactuar. These won't hide in the ground or anything, but they still have stupidly high evasion, agility, defence and magic defence. Tidus and Wakka are pretty much the only ones who can hit them even half the time, for about 60-70 damage a hit. They'll attack for around 200 damage, use their infamous 1,000 Needles for 1000 damage, or use Run Away. It's not worth going all-out to beat them, but the reward is pretty good. They appear very rarely normally, although praying at the glowing Cactuar stones dotted around Thunder Plains seems to help them appear more often. Overdrives are definitely the best way to go here, and summon overdrives can quite easily overkill them.
- Iron Men only appear in the northern section of Thunder Plains. They have 3600 HP but they're armoured, so only Kimahri and Auron can hurt them a decent amount with physical attacks. They have no elemental weaknesses (Thunder does half damage), and only succumb to darkness often if hit with Dark Buster, which you might not have. Power Break is a good idea, since their physical hit can do 700-800, and Reaper can do 600-700 to everybody. Summons can take care of them pretty quickly, otherwise just keep Auron and Kimahri out to deal damage.
