Base Class: Rogue
Whether it be through a cursed bloodline or reckless sharing of needles, you've somehow managed to breed arcane blood that courses through your veins.
Spellcasting
Spellcasting.
When you reach 3rd level, you augment your martial prowess with the arcane.
Cantrips
You learn three cantrips: Mind Sliver and two other cantrips of your choice from the sorcerer spell list. You learn another sorcerer cantrip of your choice at 10th level.
Spell Slots
The Magus Assassin Spellcasting table shows how many spell slots you have to cast your sorcerer spells of 1st level and higher. To cast one of these spells, you must expend a slot of the spell's level or higher. You regain all expended spell slots when you finish a long rest.
For example, if you know the 1st-level spell Charm Person and have a 1st-level and a 2nd-level spell slot available, you can cast Charm Person using either slot.
Spells Known of 1st Level and Higher
You know three 1st-level sorcerer spells of your choice, two of which you must choose from the abjuration and evocation spells on the sorcerer spell list.
The Spells Known column of the Magus Assassin Spellcasting table shows when you learn more sorcerer spells of 1st level or higher. Each of these spells must be an abjuration or evocation spell of your choice, and must be of a level for which you have spell slots. For instance, when you reach 7th level in this class, you can learn one new spell of 1st or 2nd level.
The spells you learn at 8th, 14th, and 20th level can come from any school of magic.
Whenever you gain a level in this class, you can replace one of the sorcerer spells you know with another spell of your choice from the sorcerer spell list. The new spell must be of a level for which you have spell slots, and it must be an abjuration or evocation spell, unless you're replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic.
Spellcasting Ability
Charisma is your spellcasting ability for your sorcerer spells, since you learn your spells through dedicated study and memorization. You use your Charisma whenever a spell refers to your spellcasting ability. In addition, you use your Charisma modifier when setting the saving throw DC for a sorcerer spell you cast and when making an attack roll with one.
Spell save DC = 8 + your proficiency bonus + your Charisma modifier
Spell attack modifier = your proficiency bonus + your Charisma modifier
Arcane Rich Strike
Your newfound link with your arcane rich veins has allowed you to tune your arcane ability into the martial, landing devastating blows on your enemies.
Starting at 3rd level, when you hit a creature with Sneak Attack, you can expend one spell slot to deal force damage to the target, in addition to the weapons damage and Sneak Attack damage. The extra damage is 2d10 for a 1st level spell slot, plus 1d10 for each spell slot higher than 1st level, to a maximum of 6d10. This damage increases by 1d10 if the creature's alignment is evil.
Clairvoyance
Utilising your ether, you can perceive future events beyond our normal sensory comprehension.
Starting at 3rd level, you can expend a 1st or higher level spell slot to add a d4 to a Dexterity(Stealth) check. The die becomes a d6 at 5th level, a d8 at 10th level and a d10 at 15th level.
Ethereal Morass
You’ve begun to allow yourself to temporarily dip into The Ethereal Plane.
Starting at 9th level, you can expend a 2nd or higher level spell slot to enter the Ethereal Plane. While in the Ethereal Plane, you can choose to do one of the following actions:
Gateway. You can use your action to summon a portal to a point you can see within 120ft and another to a point you can see within 30ft. These portals are 10ft in diameter, connected, open silently, and can be walked through, instantly teleporting any creature or object that passes through. These portals last 1 minute, can be moved vertically, horizontally and closed as a bonus action. Any attacks made through the portals are made with advantage.
Plane Walk. You can use your action to gain the Ethereal condition (detailed at the end of the doc). This condition lasts for 1 minute.
Acrimony. You can use your bonus action to force a creature within 60ft. of you to succeed an Wisdom saving throw against your Spell Save DC or take 2d4 psychic damage and become stunned until the end of your next turn. A creature has disadvantage if their alignment is evil.
Spatial Masking
At 13th level, you’ve learned to meld your flesh and bone to change your appearance.
As an action, you can perfectly replicate any humanoid. This includes their appearance, voice, size, clothing and any features unique to the creature. As well as this, you learn any information that the creature knows, up to a week in memory. To take this creature's form, you must know their name, age and must have talked to them before. This form lasts for 1 hour and can be extended by another hour if you spend another 2nd level or higher spell slot.
Marked for Death
At 17th level, you become a master of both self-tuned arcana and assassination.
On your turn, when a creature is damaged by your Arcane Rich Strike feature, you can expend a 4th level spell slot and force it to succeed a Constitution saving throw against your Spell Save DC or become Marked for 1 minute. The creature can repeat this save at the end of its turns, ending the condition. For each round Marked, the creature gains a Rancour Token, to a maximum of 4. You can expend one or multiple tokens to do one of the following actions:
Deadly Precision. As a reaction, you can expend one Rancour Token to add 10 + 2d4 force damage to an allies attack.
Death bound. As a bonus action, you can expend two Rancour Tokens to force the creature to become blind if not immune. Otherwise, you have advantage on your next attack against it.
Improved Arcane Rich Strike. The next time you damage a creature with your Arcane Rich Strike, you can deal extra force damage to the target. The extra damage is 2d8 for each Rancour Token expended. You can expend as many Rancour Tokens as you have.
Insidious. As an action, you can expend four Rancour Token and the next time you hit the creature, it counts as a critical hit.
You can only Mark one creature at a time with this feature. If the creature fails its Constitution saving throw after 1 minute, the creature becomes Marked for 24 hours. The Marked creature keeps their Rancour Tokens upon making the save.
You can use this feature a number of times equal to your Charisma bonus per short rest.