The Basilica is an LRPC (Long-Range Plasma Cannon) that can shoot targets across the map, at a high energy cost per shot. It fires faster than Cortex's Basilisk, but with less power. It also takes less space to build.

Build them to take out enemy structures from far away.

It becomes a priority target when built, so make sure you keep it safe. It can also be countered by Keepers, but at a high energy cost to your enemy.

LRPCs also make superb anti-naval gun batteries, outranging any ship or amphibious unit, even missile cruisers. They're an asset for contesting sea territory otherwise locked down by enemies.