Just got back into the game. Excited for the future changes to constellations and I'm still /patiently/ waiting for the Vesper tree. Once those are out, this build is obsolete, so for now enjoy this during the demo. I've kept the build incomplete so y'all can play around with it, but even so, with it's current setup you can continuously loop. A little in-depth, but check the bottom for tl;dr/basic guide.
First off, you're going to want to start with 'Mercy of El' passive and run 'Discipline of Pain' as your first ability. We don't really care about the first half of the ability, the second half is where it truly shines. Each attack grants (4)% stacking attack speed at (30)% at 7 stacks. At max stacks, you heal for (3.5)% of lost HP. Mercy will greatly increase survivability, especially in later rounds. Going for health upgrades will greatly increase the healing percentage rather upgrading the ability itself. Do not fear going low as you should be able to heal back to half or more after facing 2 waves. I had only a + upgrade with 1200HP and still healed to half with Nightmare scaling. Pain jumps to your enemy and attacks them with 50% attack effect. It's buffed the attack speed and will grant a stack. Pain will be your gap closer and will be considered also as an extra dodge. It comes with a built in momentum so it pairs very well with your passive. You can either use this to jump into a fight, cycle all your CDs then jump out to the farthest enemy. Or save as a dodge if you ran out.
Dodging is so important. Heavy Strike is your dodge and it's on a 3s CD. You only have two, but shields for 10% of your max HP and damages for 15% of your max HP. Going for more max HP will greatly increase survivability and could later serve as an execute or one shot on enemies. The shield is the most important part here as we will be using shields a lot. It's always imperative to save one dash for extra measures and to not panic spam. This dash has leeway with getting attacked and can be used defensively or aggressively. If your gap closer is down, dash into the enemy and start the fight with an advantage or one-shot a baby spider.
Your ultimate, or 4th ability, will only be used in the earlier rounds or until you find your main loadout. Recommended to sell for gold. The three abilities you are looking for are Ice Shield, Repulsive Shield, and Frostbite. Your basic cycle of abilities should be, Pain or Dash > (AA) > Ice Shield > (AA)2 > Frostbite > (AA)3 > AA or Repulsive. Either walk out of the fight with or without Repulsive and clear the enemies with Repulsive or dash/Pain your way out. You can also do your own cycles and play however you would like, this is just a simple combo to get the feel of the build.
Ice Shield instantly grants shield, damages your surroundings, and even heals yourself and allies. It goes insanely well with Frost essence as it'll proc with multiple hits, granting you more max HP. This will be your engage ability in correspondence with a gap closer or dash to start fights as you start with a shield and will be causing extra damage. Even with the heal being strong, do not rely on this ability to be your main healing tool. Your passive will be the number one way to heal until getting around 70%-80% HP, as the heals will become ineffective until Ice Shield is used.
Frostbite grants shield and damage on two of your autos. I recommend running Wind essence here as it helps get off those stacks and bonus damage quicker. The quicker you're able to complete the ability, the faster the CD will start. Mostly use this ability for shielding mid-fight or bonus damage. The CD is relatively low and is spammable.