Maybe messed up, I'm not entirely sure how evasion changes on Spe Pokemon in Trick Room. Just let me know if I did something wrong!

Slakoth (Laggers) M  Yamask (Cairo) M
HP: 90 (100%)  HP: 90 (100%)
Atk: 2  Atk: 2
Def: 2  Def: 3
SpA: 2  SpA: 3
SpD: 3  SpD: 3
Spe: 26  Spe: 26
Energy: 100  Energy: 100
Status: None  Status: None
Other: None  Other: None

Remoraid (QuickDraw) M  Dratini (Dovahkiin) F
HP: 90 (100%)  HP: 90 (100%)
Atk: 3  Atk: 3
Def: 2  Def: 2
SpA: 4  SpA: 3
SpD: 2  SpD: 1
Spe: 57  Spe: 50
Energy: 100  Energy: 100
Status: None  Status: None
Other: None  Other: None
Actions:
Remoraid (Move your mouse to reveal the content)
Remoraid (open)
Remoraid (close)
Water Spout CairoOctazooka CairoWater Spout Cairo
if Cairo ever uses Protect switch your attacks to Laggers!
Dratini (Move your mouse to reveal the content)
Dratini (open)
Dratini (close)
Dragon Rage Cairo  Dragon Pulse Cairo  Dragon Rage Cairo
if Cairo ever uses Protect switch your attacks to Laggers!
Laggers (Move your mouse to reveal the content)
Laggers (open)
Laggers (close)
Aerial Ace (Cairo) ~ Crush Claw (QuickDraw) ~ Rock Slide (Dovahkiin, QuickDraw)
Cairo (Move your mouse to reveal the content)
Cairo (open)
Cairo (close)
Trick Room ~ Astonish (QuickDraw) ~ Astonish (QuickDraw)
Calculations (Move your mouse to reveal the content)
Calculations (open)
Calculations (close)
Action 1:
Remoraid used Water Spout!
RNG Roll (ToCrit) [<=625 Crit]: 954/10000 (No)
(15+3+(64.5)) = 19.5 ~ 20 damage (Yamask)
7 energy
Dratini used Dragon Rage!
10 damage (Yamask)
4 energy
Slakoth used Aerial Ace!
RNG Roll (ToCrit) [<=625 Crit]: 5311/10000 (No)
(6+(34.5)) = 4.5 ~ 5 damage (Yamask)
Other Change: Mummy (Slakoth)
4 energy
Yamask used Trick Room!
Arena Change: Trick Room (4 rounds)
10 energy
Action 2:
RNG Roll (Speed Tie) [1 (Slakoth)2 (Yamask)]: 2 (Yamask)
Yamask used Astonish!
RNG Roll (ToCrit) [<=625 Crit]: 8764/10000 (No)
(4+3+(33)) = 7 damage (Remoraid)
RNG Roll (ToFlinch) [<=3000 Flinch]: 30/10000 (Flinch)
2 energy
Slakoth used Crush Claw!
RNG Roll (ToCrit) [<=625 Crit]: 3697/10000 (No)
(8+3+(33)) = 11 damage (Remoraid)
RNG Roll (ToLower Def) [<=5000 Lower Def]: 9665/10000 (No)
5 energy
Dratini used Dragon Pulse!
RNG Roll (ToCrit) [<=625 Crit]: 1731/10000 (No)
(9+3+(4.54.5)) = 12 damage (Yamask)
6 energy
Remoraid flinched!
Action 3:
RNG Roll (Speed Tie) [1 (Slakoth)2 (Yamask)]: 2 (Yamask)
Yamask used Astonish!
RNG Roll (ToCrit) [<=625 Crit]: 6380/10000 (No)
(4+3+(33)) = 7 damage (Remoraid)
RNG Roll (ToFlinch) [<=3000 Flinch]: 8667/10000 (No)
6 energy
Slakoth used Rock Slide!
RNG Roll (ToCrit (Dratini)) [<=625 Crit]: 191/10000 (Crit)
RNG Roll (ToCrit (Remoraid)) [<=625 Crit]: 6046/10000 (No)
(6+3+(33)) = 9 damage (Dratini)
(6+(33)) = 6 damage (Remoraid)
RNG Roll (ToFlinch (Dratini)) [<=3000 Flinch]: 4866/10000 (No)
RNG Roll (ToFlinch (Remoraid) [<=3000 Flinch]: 3854/10000 (No)
6 energy
Dratini used Dragon Rage!
10 damage (Yamask)
4 energy
Remoraid used Water Spout!
RNG Roll (ToCrit) [<=625 Crit]: 4542/10000 (No)
((15*.66)+3+(64.5)) = 14.5 ~ 15 damage (Yamask)
7 energy
Postaction:
RNG Roll (Moody (Stat Raise)) [1 (Atk)2 (Def)3 (SpA)4 (SpD)5 (Spe)6 (Acc)7 (Eva)]: 1 (Atk)
RNG Roll (Moody (Stat Lower)) [1 (Def)2 (SpA)3 (SpD)4 (Spe)5 (Acc)6 Eva)]: 3 (SpD)
Stat Change: +2 Atk, 1 SpD (Remoraid)
Everyone decides to beat up on poor Yamask this round, even Slakoth a little bit! If it wasn't for a crucial flinch from Astonish, Yamask would have surely fainted... I doubt it can hang on much longer. Remoraid also took a fair bit of damage, significantly weakening his second Water Spout. It all works out though, as he got a nice boost to his Attack at the cost of some SpD because of how Moody he is.
Postround:

Slakoth (Laggers) M  Yamask (Cairo) M
HP: 90 (100%)  HP: 8 (9%)
Atk: 2  Atk: 2
Def: 2  Def: 3
SpA: 2  SpA: 3
SpD: 3  SpD: 3
Spe: 26  Spe: 26
Energy: 85  Energy: 82
Status: None  Status: None
Other: Mummy (3a)  Other: None

Remoraid (QuickDraw) M  Dratini (Dovahkiin) F
HP: 59 (66%)  HP: 81 (90%)
Atk: 3  Atk: 3
Def: 2  Def: 2
SpA: 4  SpA: 3
SpD: 2  SpD: 1
Spe: 57  Spe: 50
Energy: 86  Energy: 84
Status: None  Status: None
Other: +2 Atk, 1 SpD  Other: None
Arena: Trick Room (3 rounds)