General overview

Lee's kit is an interesting grab bag of utilities. Skill 1 equips him for solo assassination missions, while skill 2 reaches its full potential with ally support. Skill 3 is his most broadly applicable skill, with both solo and team uses. His talents add even more layers to his kit and synergize well with his skills, and he has excellent offensive and defensive stats that allow him to stay on the field as long as possible. Lee is a pretty tricky unit, but he's incredibly strong (and fun!) for those who are willing to put in the effort.

E2? If you want to use him, you need to E2 him. Skill 3 is an excellent skill, and his talent 2 broadens his usage significantly.

Talents

Talent 1 (Kindness Begets Prosperity) buffs Lee's ASPD and debuffs his target's ASPD when he's blocking his target. If there are no other enemies in the 8 tiles around him, the buff is doubled. This is a very strong buff/debuff that you'll definitely notice, especially when there are no enemies in the vicinity.

Talent 2 (Preparedness Averts Peril) will consume 5 DP instead of 3 (if it's available) to block a Stun or Freeze and inflict a 3-second Stun on the attacker instead. This talent is incredibly busted and lets Lee simply ignore a lot of enemies that would otherwise be really annoying.

Skills

S1 (Stern Admonishment) is an infinite duration skill that gives Lee an ATK buff and Arts Dodge. It's good but lacks the utility that his other skills have.

S2 (Exorcise Evil) puts a Taunt mark on Lee's current target. The mark will explode after 5 seconds, dealing Arts damage to all nearby enemies. While the mark is active, every hit that allies land on the target will increase the explosion damage, up to a limit. (If the limit is reached or the target dies prematurely, the explosion will trigger prematurely.) This skill stands out from the others because it relies on team support to maximize its effectiveness - the damage is alright on its own, but it gets turned up to ridiculous if you can get the full number of stacks in. Even if you can't always max out the damage, the uptime is great, so it's a pretty powerful supplemental DPS skill if you can spare the room for it. It synergizes fantastically with high ASPD operators. This skill is also a rare source of taunt, and it's the most consistent one available, so you can strategically force your team to ignore nonessential enemies in favor of more annoying ones. It's not easy to use, but it's fun and will reward you well if you use it correctly.

S3 (Honored Guest) expands Lee's attack range to the 8 tiles around him, buffs his ATK and DEF, and every attack will push non-target enemies (force 0) away from him. Additionally, he taunts enemy attacks and gets Physical/Arts Dodge for attacks coming from outside of his range. This is a versatile skill — Lee can tear through weak mobs, duel or stall a problematic enemy while pushing everything else out of the way, take (and probably dodge) hits that would otherwise decimate your frontline... While he lacks the self-sustain that Jaye has, his high HP and the dodge allow him to survive for a while before you need to retreat and redeploy him.

Masteries

S3 is Lee's most widely used skill, but it doesn't really need masteries to function. You're already here, so you're probably going to do it anyway, and it's definitely not going to hurt him. However, keep in mind that masteries don't affect his push force.

On the other hand, S2 gets a massive damage spike from masteries, so it's definitely worth it if you use it a lot.

Modules

Module X is the more general-use Lee module because it reduces his DP tax to 2 DP instead of 3. Since Merchants take DP every 3 seconds, this module allows you to still gain DP at a reduced rate while Lee is on the field. The upgrades offer a marginal benefit to talent 2. Mod2 increases the Stun duration by a second, and Mod3 decreases the amount of DP required to 4. It's definitely not bad if you use Lee a lot, but it's not mandatory by any means.

Module Y increases Lee's ATK by 4% every time he takes DP, up to 5 stacks. A permanent 20% ATK buff is nice, especially with Lee's high base ATK, so this module is worth considering if you want him to hit really hard. The upgrades add a bit more onto the ASPD buff/debuff in talent 1, which will help him hit harder, but ultimately they're up to player discretion.