Dark Amduat (Amduat)

Amduat (Dark Horus) is a really useful unit especially in Arena Defense. He has 2 skills with Crowd Control capabilities, the first (in common with other Horus in Summoners War) is a single target hit that decreases attack bar and the second one is an AoE CC skill that decreases Attack Bar and apply two turns speed debuff on all the enemies. Despite Desert Wind scales damage with dark horus speed, it is not worth to use as a damage dealer.

The main reason why he shines in arena defense is his third passive skill, this one infact gives him an attack bar boost of 25% for each enemies' turn giving your entire team an advantage in breaking cleaver combos like Double Lushens and Tiana - Galleon . We will give you a more practical example:

Against double lushen

1) Attacker's Bernard go first boosting attack bars by 30% with his third skill 
2) Your Dark Horus gains 25% attack bar boost (in addition to the +7% of his attack speed like any other monster)
3) Attacker's Megan spreads defense and attack buff on allies + attack bar boost of 20%
4) Your Dark Horus gains 25% attack bar boost
5) At this point Amduat has even out the enemies' boosts, lushen's like other AoE nukers tend to be runed full attack so it will be easy to outspeed them.
6) Amduat takes a turn and spread is second skill (if AI works good)
7) Lushens on the other side were hitten by a slow debuff and an attack bar reduction. Your team now has to do the rest.

Sadly AI at point 6) it is not so reliable, it may fails using the first skill, but if you rune your Amduat Despair and with good accuracy you can increase his consistency. Also even if it may fail at breaking combo it works pretty well as a deterrant unit especially during rush hour.

Against Tiana Galleon teams

The process is the same and even more reliable, once tiana has stripped your team and attack bar boosted her allies, galleon will use his time to loot (so no attack bar boost in this case).

Amduat rune build

Speed Arena build: Despair/Focus or Despair/Will - SPD / %HP / %ACC or SPD / %HP / %HP with speed substat

Early game build: Violent/Focus or Violent/Energy - SPD / %HP / %ACC or SPD / %HP / %HP with speed substat