Slyvia

Slyvia is a monkey assassin mercanary that was payed the bloons to track down and kill the Super Monkey. She is the main boss of Zone 6 in my conception of Bloons Super Monkey 3. But as well, after reaching Rank 75 on my conception of BTD6, she has a 50% chance to replace Hyurandi during Hard Track Difficulty Bloonvasions. She has a variety of attacks that vary in each game.

Bloons Super Monkey 3
She is the boss of secret zone 1, Revamped Monkey Lane. She will fly (yes, fly) a little bit over the center of the screen. She will not move at all during the battle. She carries two katanas and will send thin magenta slashes at the Super Monkey in an X shape. She has 25000 HP. She has certain abilities listed here:

Katana Slash- If you get to close, she slashes you, dealing 5 HP.

Cross Slash- Sends the magenta Xs at you. Each deals 2 HP, but they come pretty fast. She fires ten then uses whip on you.

Whip- Uses her ponytail as a whip, damaging you for 8 HP, and prevents your attack and movement for 2 seconds. Be careful here.

Summon Familiar- Summons a crow at her side for fifteen seconds. She is immune to damage during this phase, and recovers health slowly. (500 every 5 seconds). The crow shoots three spreadshot, each doing three damage at a really rapid pace. The crow disappears after fifteen seconds, and the fight continues.

She will repeat this pattern until she dies. Katana Slash is not a part of the pattern, just happens if you get too close. This is a pretty dangerous boss fight, as you can lose 20 HP, by the end of the X attacks.

Bloonvasions
If she replaces Hyurandi in Bloonvasions, she has a few same attacks, but few different.

Katana Slash- Every five seconds, destroys the closest tower under any tier 4 upgrade.

Whip- Swings her ponytail, stunning all hit towers for for seconds. Ninja Monkeys are fast, and avoid this.

Mass Assassination- Swings around in three circles, with a long blade. All towers hit are killed instantly. This attack happens every ten seconds, and replaces the katana Slash on its period of time.

Cross Slash- Fires the infamous cross slashes, killing three random towers above tier 3 upgrades, but the towers cannot be tier 5. If none exist, kills the remaining number of towers under tier 3. Every eight seconds.

Summon Apprentices- Summons 20 Shadow Bloons, over 2 seconds.

Trivia
Slyvia appears to be ninja-like enough to glide through the air, as demonstrated in BSM3.

Ninja Monkeys can escape her whip attack, due to her being trained under the same training, but became unluckily for the monkeys, she became a mercenary, willing to killl her own kind.