Serpentshrine Cavern is the second tier-5 raid. Bosses there drop 250 gold, and it features one of the most challenging soloings, Lady Vashj!
All of his damage is elemental in nature: drums of forgotten kings + prismatic elixir works better than fat loot as far as damage control goes.
Now, with a prismatic elixir you shouldn't need to change phases. If you do, remember that his poison form has a very nasty debuff that reduces healing and damage done, it is better to switch back to water phase once all adds are dead.
Gear: 1/5 (the fishing pole)
You will need a fishing pole to fish him. Very easy to forget.
Jump in the water when he spouts (or run clockwise on his platform) to avoid being bumped. You can also disengage right after being bumped to, at worst, find yourself 20 yards away from land.
If fishes attack you, FD to get rid of them.
Kill the adds quickly, remeber he spouts as soon as he gets up.
You can FD to get rid of the murlocs and disengage to avoid fall damage.
In phase 1, he wil sometimes whirlwind. Cope with it. In demon form, he will hit you with a stacking debuff. But if you go at maximum range, he will hit your pet for ridiculously low damage.
Pop your cooldowns after he splits. And kill the inner demons!
Avoid the tornados. Keep the aggro of the 4 mobs on your pet.
Kill Caribdis first while interrupting her heals, then Sharkiss to get rid of his pets. Finish Tidalvess and dps Karathress down.
Gear: 5/5 (you want to one-shot elementals with auto-shot)
Strategy: 5/5 (no room for mistakes)
Phase 1: dps, keep your cooldowns.
Phase 2: Put you pet in the middle of the room on defensive (to avoid getting too far from it).
You do not want to do nothing at any given time. You must kill as many water elementals as yu can.
If a naga spawns, misdirect him to your pet.
Striders are the main wipe reason: when they are on your pet, they fear it until it gets too far from you.
If they reach you, try is over. They are slowable with concussive shot. Use dps CDs on these.
When a tainted elemental spawns, quickly find it and kill it (watch the poison bolt trajectory). If you don't, it will despawn and respawn later. Loot him, and destroy one of the pillars.
Tainted elementals = Striders > elementals > naga
Phase 3: kill any remaining adds, avoid poison patches, keep your pet alive (if you switch, remember to use deterrence, she will hit like a truck). The more buffs she has, the harder this phase is.