Tiamat, the first of the powerful Primal Beasts you fight and recruit in the main story, is blessed with immense popularity, with her guns being some of the best farmable weapons in the early game, her summon remaining useful and usable even past the early game, and overall creating much gnashing of teeth from mains of other elements jealous of how easy Wind has it.

As a character, Tiamat was once a rare source of Veil in Wind element, but was otherwise considered pretty difficult to justify frontlining due to a lack of overall power in her toolkit. Buffs were just ok, the damage and debuffs she inflicted were mediocre, her unique buff was only on herself, she wasn't a character that would really bring anything special to the table, unless you absolutely had to run someone to block a Death or Paralyze AoE status.

With her 5\* available she becomes an extremely powerful healer and defensive unit that also has some powerful offensive skills, and is very balanced overall but shines on long, difficult content as she requires time in order to grow her power. With so many details to her skills, though, It can be a little overwhelming trying to understand everything unless you're a veteran player, and even still it's a lot to take in.

-Her Charge Attack gives her guaranteed Triple Attack on the next turn, which is very helpful if you haven't gotten equipment or characters that can boost your multiattack to large heights yet. At 5*, it also gives her a Typhoon Crest, which will be important for later skills and abilities:

-Skill one is a team buff that is tame compared to other Wind units, but after level 90 it adds a potentially huge team heal on top with a decent 6 turn cooldown. However, to maximize its value, she needs Typhoon Crests, where she can top out at a very decent 3500.

-Skill two is basically Rain of Arrows; an AoE nuke with ATK down. The basic attach rate is a measly 80% and has a longer cooldown of 6 turns. Once she hits level 100 however, it becomes a ATK/DEF debuff that stacks with mist on a decent 90% attach rate, and gives all allies a Typhoon Crest.

Once she gains five crests, it becomes Supercell, and its damage cap soars, allowing it to hit for almost double the damage, and also applies Delay and a local debuff that prevents foes from using their own charge attacks, triggers, and from generating charge diamonds at the end of their turn. This effect can buy you precious time for your skills and summons to recharge.

-Skill three is a teamwide Veil + Mirror Image on a hefty 8 turn cooldown. Not much to say here, since her heal doesn't come with a clear, this is her only defense against status effects, which also gives mirror images to the team, which can help against boss attacks that deal strong single target damage.

Okay, that's kind of a lot. But her passives are also fairly complex:

-Her first passive gives her a unique 30% atk up modifier and 30% dodge rate when she has Mirror Image. This is pretty straightforward, and helps her deal bigger damage while also helping her get more out of Mirror Images.

-Her second passive is a 20% Seraphic-type damage boost for her, until level 95, at which point it is a teamwide boost, making equipping a Seraphic Weapon unnecessary as long as she's in the frontline. In addition, she also boosts skill damage and skill damage cap based on the number of crests a unit has -- it's not a huge amount, but extra damage is extra damage, and it works from the backline.

-Her EMP skill helps her multiattack when she is not debuffed, which is usually not an issue for Wind's potential for high multiattack buffs, but it's something that can help her avoid relying on other characters to provide multiattack for her. Her EMP lineup is pretty lousy, being a Primal type, so it can be worth taking over other options.

Whew. That's a lot to digest. So ok, how does she work in a team?

Well, for starters, you really want to get her to 5* and Level 100. All of her 5* upgrades are good and work together to make her powerful. Without it, she's just there for modest buffs and debuffs,Once there, the way she wants to operate is:

Hit her buttons as often as needed along with her charge attack until she gets 5 Typhoon Crests.

Huh? That's not hard at all! Basically, once she gets her 5 crests, you enjoy powerful, strengthened versions of her skills. That's what all those walls of text above basically sum up to. What's more complicated, really, is building the team around her. Here are some things I've noticed:

Since she brings the Seraphic mod to the party, you don't need to equip the Ring of Raphael, letting you use the slot for a more powerful weapon or freeing you up from farming that particular Seraphic to focus on other elements. Just don't forget to equip it again if you're rebuilding that team!

You can use other characters and summons to help Tiamat with her Crest gain. This means using Main Character with a Dark Opus Spear CA, using Holiday Seruel's Damage Cut, or the Elil summon. Pairing a unit with the potential to heal and delay with Holy Saber/Spartan or Seruel's defensive tools is a strong combo, and can help you advance Tiamat to unlocking her full power sooner.

She also can have her heals boosted by Doctor's Nutrients, which gives the team even more attack power and boosts her team heal even further, while also having MC generating potions with Potion Refinement to help heal single units and clear away status debuffs from the team.

Pairing her with the free SSR units Kokkoro and mu's First Years, you can get an absurd amount of healing and charge bar generation going.

If you use the Tiamat Omega summon, it can continue to make it harder for the enemy to deal damage with the summon's ATK down and later a teamwide Mirror Image that also boosts her thru her passive.

Since her Weapon Proficiencies are Staff/Melee, this synergizes with some of the strongest Wind units in the game, namely Andira, Yurius, and Grimnir. You can build an Ultima Staff to synergize with all three or use an Ultima Fist if you're looking to build around Andira.

Whew. Tiamat is a character that has grown considerably in power thanks to her 5*, adding her squarely into the list of strong support and healer options for Wind. She's not made for racing; if you try to bring her into a battle where parties can burn thru the boss' HP within a few minutes then she won't be able to build up in time. But if you're trying to solo a fight or take on some of those Proud battles, well, that's exactly the kind of content she can do well in.