I just came up with a strategy to defeat Ygg without using Tiamat magna, Chieftain's break assasin, Gawain's shield or Rena's heal. Hopefully it is helpful to those who are playing without these end-game stuff or gacha luck.
(*Note: This guide does not apply to players with SSR wind team or Tiamat magna weapon pool)
Below are my setup:
1. Dark Fencer with Centurion as EX (to DODGE Ygg's ougi)
2. A team of charas with EVADE skill: Stella, Asuteru, Rosetta, Feena etc.
3. Saggittarius and Anat as main and support summons (or 2 Anats).
4. One or two weapons with 背水 skill (since we have no heal here, we'll need to boost our dmg as our hp getting lower and lower, I'm using Celeste spear.)
5. A weapon pool with lv3-5 wind weapons. (I only have 4 usable wind weapons in my pool T_T)