Rogue subclass
Assassin
Infiltration, poison 
D&D Portal - Poison Damage type Poison is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/poison/, disguise, and devastating opening attacks.
Assassin starts by changing the normal Rogue play pattern through Bonus Proficiencies; Assassinate, giving the subclass its first clear mechanical identity.
Later features such as Infiltration Expertise, Impostor, Death Strike expand that identity at higher levels, so the subclass has a clearer role in combat, exploration, utility, or support.
Bonus Proficiencies; Assassinate
3rd level
Gain disguise-kit and poisoner’s-kit proficiency, advantage against creatures that have not acted, and automatic critical hits 
D&D Portal - Critical Hit Combat rule Critical Hit is a combat rule used by attacks,
damage, defenses, or turn order. Full link: https://dnd-portal.com/rules/combat/critical-hit/ against surprised targets.
Infiltration Expertise
9th level
Create a convincing false identity with time and money.
Impostor
13th level
Mimic another person’s speech, writing, and behavior after studying them.
Death Strike
17th level
A surprised creature hit by you must save or take double the attack’s damage.
FAQ
What is the Assassin Roguish Archetype?
The Assassin is an ambush and infiltration Rogue whose strongest combat feature rewards acting before enemies and attacking creatures that are genuinely surprised. At Rogue 3, Assassin layers ambush and infiltration tools onto the normal Sneak Attack and Cunning Action chassis; when surprise is unavailable, the character still functions as a full Rogue.
Read more: Assassin 
D&D Portal - What is the Assassin Roguish Archetype? Assassin FAQ The Assassin is an ambush and infiltration Rogue whose strongest combat feature rewards acting before enemies and attacking creatures that are genuinely surprised. At Rogue 3, Assassin layers ambush and infiltration tools onto the normal Sneak Attack and Cunning Action chassis; when surprise is unavailable, the character still functions as a full Rogue. Full link: https://dnd-portal.com/faq/assassin/what-is-the-assassin-roguish-archetype/
What are the main Assassin features?
Assassin is built around ambushes, disguise, and first-round lethality. Assassinate rewards acting before enemies and becomes devastating against creatures that are actually surprised, while later features build false identities, imitate other people, and turn a successful surprise attack into an even more dangerous opening strike.
Read more: Assassin D&D Portal - What are the main Assassin features? Assassin FAQ Assassin is built around ambushes, disguise, and first-round lethality. Assassinate rewards acting before enemies and becomes devastating against creatures that are actually surprised, while later features build false identities, imitate other people, and turn a successful surprise attack into an even more dangerous opening strike. Full link: https://dnd-portal.com/faq/assassin/what-are-the-main-assassin-features/
How do you build and play a Assassin Rogue?
Build the Assassin on top of a normal Dexterity-focused Rogue, then invest in the secondary abilities and skills that support the archetype. Coordinate with the party before combat. The Assassin is at its best when stealth, scouting and encounter setup allow surprise to occur. Once combat has started, it is still a normal Rogue with Sneak Attack, Cunning Action, Expertise and defensive features even when Assassinate's surprise clause cannot be triggered.
Read more: Assassin D&D Portal - How do you build and play a Assassin Rogue? Assassin FAQ Build the Assassin on top of a normal Dexterity-focused Rogue, then invest in the secondary abilities and skills that support the archetype. Coordinate with the party before combat. The Assassin is at its best when stealth, scouting and encounter setup allow surprise to occur. Once combat has started, it is still a normal Rogue with Sneak Attack, Cunning Action, Expertise and defensive features even when Assassinate's surprise clause cannot be triggered. Full link: https://dnd-portal.com/faq/assassin/how-do-you-build-and-play-a-assassin-rogue/
How does Assassin interact with Sneak Attack?
Assassinate can make the first-round Sneak Attack much more dangerous. Advantage against a creature that has not acted can satisfy the normal Sneak Attack requirement. If the target is actually surprised, the entire qualifying hit becomes a critical hit, which doubles the attack's damage dice, including Sneak Attack dice under the normal critical-hit rule.
Read more: Assassin D&D Portal - How does Assassin interact with Sneak Attack? Assassin FAQ Assassinate can make the first-round Sneak Attack much more dangerous. Advantage against a creature that has not acted can satisfy the normal Sneak Attack requirement. If the target is actually surprised, the entire qualifying hit becomes a critical hit, which doubles the attack's damage dice, including Sneak Attack dice under the normal critical-hit rule. Full link: https://dnd-portal.com/faq/assassin/how-does-assassin-interact-with-sneak-attack/
How does Assassinate work with surprise?
Assassinate has two separate 2014 benefits: you have advantage on attacks against a creature that has not yet taken a turn, and any hit you score against a creature that is surprised is a critical hit. Acting before a creature is not the same as that creature being surprised; surprise must be established when combat begins under the normal surprise rules.
Read more: Assassin D&D Portal - How does Assassinate work with surprise? Assassin FAQ Assassinate has two separate 2014 benefits: you have advantage on attacks against a creature that has not yet taken a turn, and any hit you score against a creature that is surprised is a critical hit. Acting before a creature is not the same as that creature being surprised; surprise must be established when combat begins under the normal surprise rules. Full link: https://dnd-portal.com/faq/assassin/how-does-assassinate-work-with-surprise/