Peitsivartija

The Lance Sentry (in-game name Peitsivartija) is a large robotic sentry mainly found in The Vault, and occasionally in the Underground Jungle. It has a thrown lance attack that deals heavy damage and extreme knockback, which can send the player flying several screens away unless stopped by terrain.

Behaviour & Combat
Like other robotic enemies, it is heavily armored and resistant to most attacks. Due to its large size, it has a problem fitting into tight spaces and can usually be shaken off rather easily by a fleeing player. If it sees the player, it will give chase and throw its lance from medium range (about half a screen). If it takes a lot of damage at once, it may flee.

Unlike other robotic enemies, it is completely immune to explosions. Combined with its natural resistances as a robotic enemy, this makes it extremely resistant to damage, being primarily vulnerable only to electrical damage.

Projectiles that deal a lot of damage in a single hit are preferable to fast-firing low damage wands due to its naturally high resistances. Lightning Bolt's range is a little low and its main damage source is explosive rather than electrical, so it will be less effective than normal, but can do the job if you can land enough hits. If you must use a fast-firing wand, consider adding Electric Charge for additional damage and the added stun effect. Keep your distance as much as possible and watch for their throwing animation to avoid getting hit with their lance attack. Melee combat is not recommended.