Engineer

Engineer is a playable character in Risk of Rain 2.

How to Unlock
The Engineer is unlocked upon completing the Challenge "Engineering Perfection" (Complete 30 stages.)

Tips

 * Getting several Bustling Fungus and stacking TR12 Gauss Auto-Turrets on top of each other is a great way to cheese certain bosses. This isn't as effective on the Magma Worm as it tends to knock the Engineer out of the healing radius or outright destroy the turrets, but the Turrets' auto-aim may make this boss easier to fight nonetheless.
 * Getting plenty of AoE and/or proc items for your TR58 Carbonizer Turrets (like Sticky Bomb, Ukulele, Will-o'-the-wisp, Sentient Meat Hook, etc.) and some healing items for the early game (like Monster Tooth) will turn them into fairly self-sufficient powerhouses. If you manage to get the right items, both damage and defense wise, these turrets will pretty much clear stages by themselves!
 * A single Hardlight Afterburner can allow for 100% uptime of Bubble Shield.
 * Stacking Bandolier can lead to a constant up time of your Bubble Shield, allowing for good cover from Wisps and Titans/Colossi as the game progresses. It also proves useful to refresh your Turrets' cooldown, giving you a backup in case one of them gets destroyed.
 * Both Pressure Mines and Spider Mines can be stuck onto the outside surface of the Bubble Shield. Crowbar is highly useful for both mines.
 * Placing Spider Mines on elevated positions may allow them to jump onto airborne enemies. Similarly they can be placed onto NPCs and other survivors in a coop situation unlike the immobile Pressure Mines.
 * Leeching Seed is a high priority item, as it heals your Turrets as they deal damage. They're particularly useful on the more rapid firing TR58 Carbonizer Turrets.
 * Alternatively, stacking Lens-Maker's Glasses (at least 10 stacks are needed for guaranteed critical strike on hit) and Harvester's Scythe (one stack can provide the same amount of healing as 8 stacks of Leeching Seed) will grant much greater healing from dealing damage at the cost of a greater item investment. This works exceptionally well when combined with items that proc from critical strikes such as Predatory Instincts (an item that increases attack speed, allowing for even more rapid healing).
 * Due to their faster firing speed, TR58 Carbonizer Turrets are better at proccing certain item such as Tri-Tip Dagger, Stun Grenade, Sticky Bomb and Shattering Justice. Soldier's Syringe and 57 Leaf Clover may improve them further (though these are universally good on both turrets).
 * Due to the AI behavior of TR58 Carbonizer Turret, Focus Crystals might be useful when they eventually haphazardly charge into enemies. A Genesis Loop and a few Topaz Brooches or Monster Teeth can allow them to turn this caveat into a positive.
 * Do note that only Paul's Goat Hoof and Red Whip increase the movement speed of TR58 Carbonizer Turrets as they never sprint. Hopoo Feather will grant an additional jump, but the turrets will use all of the jumps immediately whenever they jump so each feather only provides a small boost to jump height. This can also lead to turrets taking excessive fall damage if they jump too high.
 * You may sprint while Bouncing Grenades is charging up. Deploying Bubble Shield will not stop sprinting.
 * Acquiring Rejuvenation Rack, N'kuhana's Opinion, and as many Bustling Fungus as possible will allow the stationary TR12 Gauss Auto- Turret to spawn many of the flaming skull projectiles as you and both your turrets will all heal each other (causing N'Kuhana's Opinion to continuously proc).
 * TR12 Gauss Auto-Turret and the TR58 Carbonizer Turret will not receive new items their Engineer picks up after deployment. Their items are only updated upon redeployment.
 * Both turrets greatly benefit from Dio's Best Friend as the 3 second invincibility time will always reset on newly deployed turrets as long as the Dio's Best Friend has not been used up on the Engineer himself. This is an especially important item during Monsoon runs.
 * Bandolier can be used to offset the long cooldown of the turrets, though TR58 Carbonizer Turrets can pick the ammo packs up by walking atop them. This may not be a problem if you and your turrets have Visions of Heresy.
 * The TR58 Carbonizer Turret still benefit from attack speed even though they shoot laser's, i.e. 1 Soldier's Syringe makes them go from 2-3 hits per second to 4-5.

Trivia

 * Engineer was one of the playable characters in the first Risk of Rain.