Loki is the Norse god of mischief and evil and the adopted son of Odin All-Father, the ruler of Asgard. He is crafty, clever, and resourceful, using sorcery to achieve his intricate goals.Marvel Source
Loki resents the glory and acclaim given to his adoptive brother, Thor, and he strives to place himself on the throne of Asgard. However, on the rare occasions when his goals overlap with Thor or other heroes, Loki has been known to ally himself with those he would otherwise detest.
Items
To maximize the effectiveness of this build, a significant amount of luck is required, mainly due to the fact that Loki's uniques are very specific to the tree that they represent. We are playing a primarily Son of Jotunheim build, and therefore Crown of Lies is borderline useless for us. For the following section, I will be referring to Slots 1-5, as seen on your character sheet from left to right.
1: You really only have 2 reasonable options here: Lævateinn and the Darkhold. Darkhold>Laevetinn IF you can get it, but that's not always an option. Lævateinn is good if you can get a high +Mental Damage and Arcane Binding roll, and no Cosmic will come close to the damage you get from it. Still The Darkhold is your #1 option for this build.
2: Armor of Invincibility is your only real option here. Farm it, use it.
3: Ikol. It's amazing; spirit cost reduction, crit, crit damage, etc. It's a good item, and the cost reduction is a must-have for Loki.
4: I'd use a well-rolled Cosmic in this slot. The Golden Apples of Idun are mediocre at best. Get something with + to Unyielding, Permafrost Spikes, and/or Jotun powers. Aim for HP and Crit as your other affixes. Keep an eye open, you'll get something.
5: Cerebro Remote Interface if you can get it, otherwise grab a Cosmic. The Crown of Lies is a joke, and nobody should use it.
Core
ONLY USE +INT IF YOU HAVE CEREBRO
There, now that that's taken care of, the +Int core I use is only there to acquire the Unearthly level of Int, granting +10% attack speed.
+25% Spirit and HP on Medkit is a must if you're using any Runeword but the River Soul, but it's still nice to have regardless. I recommend it highly.
+HP, Lifeleech, or Invincibility on Medkit are decent alternatives to Int if you're lacking a Cerebro.
Energy and Durability would be a waste; you're already at the highest level you can reach without hitting DR if you have Laevetinn/Darkhold and the Armor of Invincibility. (Trust me on this, the values on Marvelbase are off)
Medallion
I use a Cosmic Wizard; all of our spells are Ranged and Mental, so it's not bad. Doc Oc is another good option.
Relic
[item]214[/item]or [item]190[/item]. All of your spells are Area AND Ranged, save for Ice Fissure (Frost Giant Form), which is Ranged only. Still, the values on [item]214[/item] are higher, so I use it.
Legendary
The Warlock's Eye is your best bet. Gungir's a decent alternative.
Uru
+Mental Damage. Defense if you feel you need it (but I doubt you will).
Artifacts
I use [item]95[/item], [item]198[/item], [item]223[/item], and the Mental Focus Headband.
Nobody would fault you for exchanging something for an [item]234[/item], Gem of the Kursed, or even [item]247[/item] if you need survivability, but the setup listed above is what I found the most success with.
Blessings
Fandrals or Helas. It's really preference here. I use Hela, and I feel like if you have Bowazon, then Hela is a better option, but Fandral's definitely nice.
Ring
Cosmic with HP, Crit, Ranged, and/or Area. If you can't get all of those, that's fine, just try to get as close as possible.
Insignia
O'Grady or Valk take the cake for Loki; he's kind of limited now that they "removed" Fantastic Four from his set. Try to get a combination of Area, Ranged, HP, and/or Crit on an Epic one.
Runes/Runewords
Tyr for slots 1 and 5. Cattle for 2-4. HP is good, and Loki needs all the crit he can get.
My personal recommendation is Bowazon for a runeword. It's an absurd amount of Ranged damage (all our spells are ranged), Crit (which we need), and Brutal (which we also need).
An alternative, or one to get while you farm for Bowazon is the River Soul, it's cheap, a phenomenal amount of Spirit Regen, and you'll never be left wanting for Spirit.
Not really a huge fan of the Storm Giant for Loki; the only spell that benefits from +Duration (and it's only +4) is Arcane Binding. The proc is nice, but it'll only be active 1/6 of the time. It's not BAD, it's just not ideal in my opinion.
Abilities
Son of Jotunheim
1 point in this. Your +skills will bring it up nicely.
This is your main damaging ability. Max it. Marvelbase didn't update it, but it also applies vulnerability.
Max this. It's crazy damage, and the duration is extended solely through levels.
Max it. 1k+ damage at all times? Yes please.
A point of contention amongst Loki players. I max it because it's a massive amount of health regen. Try maxing it out and you'll definitely notice it saving your life.
Sorcery
Max it. HUGE cost reduction, max spirit, and duration.
Put any remaining points into this spell. It's definitely good, and can be maxed as an alternative to if you're more into defensive stats. (The Projectile Reflection is nice.)
This is your second highest Damage Per Cast ability (Behind ). Use it every 6 or so seconds to ensure it's always up, and you're golden.
Mischief
Another 1 point wonder. Your +skills will bring it up to the point where it's significant.
Disregard all other skills.
"But Caedos, why don't you max ? It's overpowered."
Yeah, it's good, but only when there's 2-4 enemies nearby with relatively high health totals. It's beastmode in MM, and on specific X-Defense waves, but the situations wherein it's more beneficial than Permafrost Spikes are too limited to warrant getting it over passives that will better maximize your damage in single target or mass AoE situations.
Skill Usage
Trash
Pop and teleport around the Terminal. Even in Cosmics, with good enough gear, this spell has enough power to kill any non-boss is a matter of seconds. You can easily rack up to 75 kills in one use.
When is down, just spam while keeping up on Blues/Yellows.
Bosses
Use off the bat, and Frost Giant Form (FGF) immediately afterwards if you feel it's necessary. FGF will enhance your damage and will take down the bosses in no time. If you don't want to use FGF, then be sure to keep up and spam . Use on cooldown if the boss doesn't die within the duration of the first one (Lookin' at you, Doom).
Using Frost Giant Form:
Rain of Shards is your #1 priority in FGF. It's insane damage, keep it up. Frost Smash is decent now that it's fixed, but not really worth using in against a solo boss like Doom; only use it if you're surrounded by mobs. Ice Fissure is an absurd amount of damage; it shoots 3 shards out, and if you're close, all 3 will hit and can totally shred a boss. Now that Frost Orb has been fixed, it's higher DPS than your punch, so use it liberally when RoS and IF are on cooldown.
BE CAREFUL IN FGF! You aren't very tanky in Frost Giant Form; you get +2% Damage Reduction and +50% HP, which is not enough to survive much. Your attacks are slow, and you have low mobility, so watch your positioning.
Playstyle
You are a mobile AoE caster. You have clones to soak damage, an invisibility and teleport (which can be used while CCd) to get away from trouble, and you have an AoE damage ability that heals you when it hits chilled targets. If you die, it's your own fault. Plain and simple; if you died, it's because you LET something get too close, or you stood in something bad. I have my fair share of defeats on Loki, but those are due to mistakes I've made. This build is not a tank build, you are RELATIVELY squishy, but you're still tankier than most other casters, and even a fair share of dodge heroes. Use your mobility to your advantage and you'll have no problems with any of the current content.