Amearin will 5ft step to M/20 and begin casting
Summon Monster I to summon a
celestial eagle into melee range of Shukak.
Amearin HP 14/23
The centipede will do its best to keep damaging the swarm in S/24 with its smite evil ability:
bite
(1d20+4)[10], dmg
(1d6+2)[7] plus poison, cc
(1d20+4)[19], cdmg
(1d6+2)[3]
Giant centipede HP 1/7
The spider swarm appears in F/19 and goes after the nearest living thing, which is the worm swarm in F/20. It moves into F/20 (can two swarms share a square?) and does
(1d6)[2] swarm damage to the worms. (I'm guessing they're immune to the poison and distraction effects.)
After this the spider swarm isn't under Amearin's control, and will mindlessly move to attack the nearest target. (Hopefully that's the other swarm in I/18 and not one of us!)
Spider swarm HP 9/9
Create Pit round 4/6
Summon Monster II (centipede) round 3/5
Summon Swarm (spiders) round 1/5