Okay so I'm about to head into Tier 5 and have no idea how to upgrade my set for it. What I have right now: Also, scrollwise, I currently have a Terra Focujin and a Cobalt Eternal, but I have no idea what to add to round it out a bit or if anything needs to be changed to whatever.

Hi! Your set is very good as it is. There are a few improvements you can make though.

Swap Icy Freezing Rod of Doom for a freezer. It's a cute weapon but the freeze on it is too unreliable. If you're spending 5 turns trying to get one freeze then you either die or could have beaten the opponent without it anyway. The cheapest freezer is Bottled Ice (300k) which is fairly high, ~90% chance I think. When you have enough hard tokens from the battle shop - you might already - you should get a Gorgun. That has a 100% chance to freeze.

Rainbow Quill is probably at the stage where it's no longer useful. Long-term you should aim to replace it with a blocker (Shinwas Temple Shard or Rainbow Vortex). They are especially useful against opponents that have healing disabled like Daemon.

Mystical Star Shuriken can be upgraded to an Iron Fireside Lantern. They're available in the Millionaire Center in about 4 months from now. It's a much better bomb and also doubles up as an item that unlocks a challenger. A good investment.

Your Replica Minotaur Knocker is good but the Malevolent Grimfruit will need to be upgraded soon. I think you have two real options depending on how patient you are. You can end up with a Reborn Icewand of Doom (T6) or an Arrow Harpoon (T7). The Reborn Icewand of Doom is made by combining 2 Millionaire Center items together. The Freezewand of Doom (10m) is available now and will be available until the 21st of March. It's a T5 weapon so you could start using it now, although it's about the same as the Grimfruit. The 2nd part, Reborn Wand of Doom (also 10m) will be available in 4 months. It's probably the best T6 weapon and still useful until about T8. The Arrow Harpoon is 10m in shops but has just been newly released, the price will go down. It heals 100 HP flat each turn which for a T7 pet is like 12%. Only downside is you'll have to wait a while to use it.

Your scrolls won't need any work unless you have spare AP and cash to spend. A Morosbane Scroll is 20m in shops and costs 15 AP. It would be the ideal thing to round out your scrolls. Does 40 icons and heals 300 HP once per battle.

Hope it helps :)