As Terran
Make:
Viking
MarineMissile TurretTarget the Prism first; without warp-ins, the ground army trades worse.
Open in the counter tool with Warp Prism tagged ->As Protoss
Make:
Stalker
Phoenix
ObserverBlink or Phoenix pressure forces Prism micro instead of perfect pickups.
Open in the counter tool with Warp Prism tagged ->As Zerg
Make:
Queen
Hydralisk
CorruptorCreep vision and anti-air near tech structures stop repeat warp-ins.
Open in the counter tool with Warp Prism tagged ->
Zealot
Adept
Sentry
Immortal
Colossus
Disruptor
High Templar
Archon