Fairies

==What are the best fairies?==
*Disclaimer: This section has been written pre-SSS Costume patch.
The 2 staple fairies that you will have with any weapon and playstyle are Glacio and Olla (SS only for Olla)
The third fairy will depend on your weapon and current activity, all of the weapons except the Sword use Nix when you want to farm, it makes the clears faster, the exception to this is the sword where Yeti is a good alternative to Nix.
When you want to push higher and deal the maximum damage, use Yeti for the Sword, Nix for both the Bow and Dagger and Sinbad for the Staff.
If you are still in the early game with the dual weapon, Aqua is very good there as well.
==With the introduction of SSS Costumes and Boss Rush (VIP 14)==
Passive stats provided by Spring SSS Costumes (Patch 1.2.40) demonstrate better synergy with some fairies, when combined properly, both shall aid you to clear boss stages within 5 secs even at higher stages (9000+). At updated VIP 14 (Patch 1.2.50), if you kill the boss in 5 secs you shall fight the next boss immediately saving you a great deal of time for key farming. 
 May-15 Update: As per TDS Discord community consensus, SS Nix happened to received a lot of positive feedbacks from end-game players (including GreatSword users) as an all-rounder fairy for each weapon and daily tasks/purposes. Hence, merging of only one fairy lineup for daily tasks for all weapons. Added Greatsword+Staff dual optional lineup.
Fairy Guide v1.0.5
Compiled by: RyuJin
==Fairy Exploration==
There are 5 grades of fairy explorations, C, B, A, S, and SS. S grade exploration requires an S grade fairy while SS grade exploration requires an SS grade fairy.
During the early stages of your game, you may encounter issues of not being able to complete your fairy exploration because you have pushed to level 4500 too fast. Even if you do not have the fairies, it would still be recommended to continue pushing or farming relics because fairies will not have a big impact at your current level.
 Note: SS fairies can't be used as a placeholder for an S grade fairy. Similarly SSS fairies cannot be used. Certain exploration quests require region-specific fairies.
==Purchasing Fairy Package==
It may be considered useful to purchase either 1x SS fairy or 2x SS fairy using real money to use for SS grade fairy explorations. Purchasing the fairy during the first/second week of your gameplay will enable you to participate in SS fairy exploration quests much faster. However, this is up to your own decision as you may be feeling lucky and pull a SS fairy from the fairy cage. On the other hand, it could potentially take up to a month and a half for your first SS fairy.