Sirin Ascendant - Honkai Queen is the signature set of the first playable Herrscher in the game - Herrscher of the Void (HoV). Currently, you can get Sirin Ascendant from Exchange Shop and gacha.
 Sirin Ascendant full set is specialized for HoV, providing bonuses that match her mechanics. It gives her the most damage output and accelerates her attack cycle, sp gain and Herrscher Charge gain.
 Sirin Ascendant M reduces evasion skill cooldown. Can be used on Knight Moonbeam and Drive Kometa for time fracture support in Memorial Arena.
Sirin Ascendant T is specialized for HoV, providing her 50% Physical DMG during Herrscher Form. Not recommended on other battlesuits as 20% Physical DMG is just decent.
Herrscher of the Void gains 30% Crit DMG and her Evasion CD is reduced from 20 to 16 seconds. Crit DMG is self-explanatory. Evasion CD reduction accelerates her attack cycle and Herrscher Charge gain.
In Memorial Arena, Knight Moonbeam and Drive Kometa can benefit from evasion cd reduction, allowing them to trigger time fracture more frequently.
On Herrscher of the Void, the increase in attack speed accelerates her damage output, sp gain and Herrscher Charge gain. Also it feels much smoother operating her. 15% Physical DMG is just the icing on the cake.
Image shows Space Shield effect with different HoV outfits
Sirin Ascendant B is a one-of-a-kind stigma that gives both physical damage and atk speed in one slot. Generally any physical damage dealers can use it, preferably against enemies without elemental damage.
Herrscher of the Void can easily reach max stacks by summoning Space Core (friendly entity). A red aura will appear at the lower part of the character while the buff is active.
HoV can summon Space Core with
Additionally, her new PRI-ARM Domain of the Void summons even more cores.
Image shows HoV's Space Core. The red aura at HoV's legs indicates that the buff is active.
With full set, HoV gains 80% Crit DMG. HoV herself already has a lot of built-in crit damage. With sss-rank leader skill and Domain of the Void, she will have 150% bonus Crit DMG. The number is definitely high. 15% Crit Rate is very valuable since s-rank HoV lacks crit rate outside of ultimate.
Overall, full set provides a lot of unrestricted multipliers, which means HoV's Basic ATK, Ultimate and weapon skill enjoy most of the bonuses from Sirin Ascendant.
Simple bonus multiplier calculation of HoV full set, with lead skill and Herrscher Form:
Only Herrscher of the Void can take advantage of Sirin Ascendant set. It provides her with the most damage output and accelerates her attack cycle, sp gain and herrscher charge gain.
Knight Moonbeam and Drive Kometa can use Sirin Ascendant M in Memorial Arena. Evasion cd reduction allows them to trigger time fracture more frequently.
 HoV clearing Abyss mobs:
 HoV vs RL Double Wendy [YOUTUBE] [BILIBILI]
 HoV vs RL Titan + Hierophant [BILIBILI]
 HoV vs EX Tonatiuh 30826 [BILIBILI]
 HoV vs EX Kallen 30133 [3RDGUIDE]
 SSS-rank HoV vs EX Tonatiuh 31306 [BILIBILI]
 KMB with Sirin Asc M [YOUTUBE]
SHOULD YOU GET SIRIN ASCENDANT?
With her new pri-arm Domain of the Void and the new physical support Starlit Astrologos, HoV has become stronger than ever. Full gear S-rank HoV is capable of clearing even the hardest abyss mobs, and get high scores against certain Abyss bosses. Her score in Exalted Arena is above average.
If you have Herrscher of the Void AND plan to use her as physical damage dealer, then you may consider getting Sirin Ascendant from gacha or Exchange Shop.
Sirin Ascendant full set is specialized for HoV. She requires the set to reach maximum potential as a damage dealer. It is recommended to get Sirin Ascendant if you have Herrscher of the Void AND plan to use her as physical damage dealer.