There are 2 main strategies right now for defeating The Seven Deadly Sins: Grand Cross Guild Boss. One is with GOwther, one is without Gowther.
The Seven Deadly Sins: Grand Cross Guild Boss – Basic Requirements
Whatever strategy you are using, you want to have Green Jericho in your team.
Also, equip the Attack/Crit Damage set on her with Attack and Crit Damage sub stats.
The best food is Crit Damage Food.
If you are facing it hard to deal with the Guild Boss, you might want to replace your buff Hero (Like Helbram, Gilthunder, etc) with Arthur as he gives you a bit more survivability while still offering a decent amount of damage.
Defeat Guild Boss using Gowther
Place Gowther in position 1 of your team like this:
| Slot 1 | Slot 2 | Slot 3 | Slot 4 |
 | |   |   |
Helbram is better for damage.
Turn 1: Spend your useless cards like Jericho’s Attack, Gustaf/Merlin’s Attack or Gilthunder/Helbram Attack.
Turn 2: You should get an extra rank-up card now. Combine it with the previous one for level 2 rank-up card. Combine Gustaf’s Freeze and Helbram’s buff in this turn and use Jericho’s attack card to stack her damage more. You want to reset here if the RNG god doesn’t like you.
Turn 3: Get the last Ultimate Gauge Orbs for Jericho.
Turn 4: Use Helbram Buff then use freeze and Jericho Ultimate.
It is also viable to try to get the Gowther level 3 buff when using Helbram but it requires a lot of RNG and you want to restart for a few times.
Defeat Guild Boss without Gowther
If you don’t have Gowther or just don’t want to use him, this is another strategy for you!
Place Jericho on the first position of the team like this:
| Slot 1 | Slot 2 | Slot 3 | Slot 4 |
| | | |
Turn 1: Remove the useless cards: Gustaf attack, Merlin attack, Gilthunder attack, Jericho attacks, etc.
Turn 2: Try to combine four cards so you will get level 2 of debuff or freeze. You will be able to use either Gilthunder Buff + Freeze or Freeze + Helbram Buff)
Turn 3: Try to get as many Ultimate orbs on Jericho as possible using her attack card while trying to get level 3 Freeze. You want to reset the battle here if the RNG god doesn’t like you
Turn 4: Combine for level 3 Freeze while getting Jericho’s Ultimate ready.
Turn 5: Use Helbram/Gilthunder level 2 buff and level 3 Freeze then use Jericho Ultimate.
Easy right? Good luck and have fun defeating the Guild Boss!
When the boss is going 1st and hits you and your characters are 50% health left good luck with it! 😀
U need more CC (power) than the boss, else dont even try.