Great Nailsage Sly

Great Nailsage Sly is a quest boss in Hollow Knight introduced in Godmaster. He sits at the top of the Pantheon of the Sage in Godhome.

Behaviour and Tactics Phase 1
 * Slash Combo: Great Nailsage Sly slashes twice in quick succession towards the Knight. The first slash is an overhead, downward slash and the second is an upward, overhead slash. Both slashes cover the entirety of Sly. He shifts forward a little with each slash. There is about 0.5 seconds between these slashes. Sly changes directions between slashes if the Knight ends up on his other side before the first slash is over. If the Knight is close to Sly after those two slashes, he follows up with a final, special attack (again about 0.5 seconds after the previous slash). Sly does a short leap into the air at a forty-five degree angle towards the Knight. During this ascension, Sly flips around with his nail out, becoming a flying circle of death. He flips like this for about 0.75 seconds. He stops flipping as he returns to the ground.
 * Nail Slam: Sly leaps into the air, coming up short on the Knight's position, does a flip, then slams down with his nail. The nail strikes where the Knight was when Sly jumped. Often times, after Sly lands, he follows up with an upward, overhead slash.
 * Great Slash: Great Nailsage Sly performs the Great Slash Nail Art. He takes about 0.75 seconds to charge up this attack. He may approach the Knight before charging up. The range on the Great Slash is much longer than Sly's nail. This attack deals two Masks of damage.
 * Dash Slash: Great Nailsage Sly performs the Dash Slash Nail Art. He takes about 0.75 seconds to charge up this attack. Sly charges this attack up in a corner of the arena and leaps to that corner. He dashes across about 75% of the arena and the slash covers the rest. This dash occurs in about 0.33 seconds. The range of the slash is much greater than Sly's nail.
 * Cyclone Slash: Great Nailsage Sly performs the Cyclone Slash Nail Art. He starts by leaping into the air and charging up while he is mid-air. As he spins, he floats to the ground towards the Knight. This attack lasts for about 2 seconds. He takes about 0.75 seconds to charge up this attack.
 * Sprint: Sly runs towards the Knight when they are too far away to perform an attack.

Phase 2
 * Frenzy: Great Nailsage Sly dashes around the arena 2 to 5 times before flipping around rapidly with his nail. The end of this attack is a modified version of what Sly does at the end of a full Slash Combo. In this version, Sly moves laterally towards the Knight a short distance; the flipping lasts for only 0.5 seconds; and he prefaces the flipping with a single flip and a pause. After he's done flipping with his nail, Sly flips one more time and then starts the whole process again. This is the only attack in the second Phase.

Great Nailsage Sly is the final boss of the Pantheon of the Sage, the third of five Pantheons. He is significantly more agile than most of the other bosses in the game. His nail's natural range is equivalent to the combination of the Longnail and Mark of Pride Charms.

There is time to attack Sly in between his attacks but that time varies from 0.5 seconds to 2 seconds depending on the combination of attacks.

It is important to maintain good spacing against Sly and keep watch of the Shade Cloak cooldown as shadow dashing is exceptionally useful for surviving the fight against Sly. The Sharp Shadow Charm increases the distance of the shadow dash and allows the Knight to even safely dash through the Cyclone Slash attack. The Sprintmaster Charm allows the Knight to run safely away from many of Sly's attacks, allowing them to save shadow dashing for absolute emergencies.

The Vengeful Spirit/Shade Soul and Desolate Dive/Descending Dark Spells have the most utility against Sly. Howling Wraiths/Abyss Shriek is very useful in his Cyclone Slash attack, as the Knight can get one Nail hit before he releases it then quickly use Howling Wraiths/Abyss Shriek up to 3 times (4 with the Spell Twister Charm), this deals enough damage to almost finish the first Phase.

Healing without Charms is safest when Sly is staggered and during the transition from Phase 1 to Phase 2. However, the Knight can heal without Charms if they are quickly safe from the third attack of the Slash Combo or just out of range of the Nail Slam (prompting the follow-up attack). The Quick Focus Charm makes those moments safer for healing and increases the Knight's healing capability during a stagger or Phase transition from 2 Masks to 3. To further increase safe healing opportunities, combine the Shape of Unn Charm with Quick Focus. In all cases, it is best to start healing as soon it is safe to do so.

It is recommended to stay away from Sly throughout the entirety of the Cyclone Slash attack as all offensive options are risky. It is recommended to stay on the ground when Sly uses the Great Slash attack because the aerial hitbox of Great Slash is much larger than the attack looks. There are no special recommendations for dodging the Dash Slash attack.

For the Frenzy attack, the most consistent tactic is to stay near the middle of the arena and wait for Sly to slow down. Once he slows down, the spin happens quickly so get out of his nail's range and turn around to strike him either with the Nail or a Shade Soul (there are other useful options, including Sharp Shadow). Repeat this process until Sly is defeated.

Variations

Achievements

Trivia
 * In the Nintendo Switch reveal trailer, Sly's arena had a more light yellow background like Paintmaster Sheo and Brothers Oro & Mato, as opposed to the darker background the arena has in the final version.
 * Sly seems to be using the Nailmaster's Glory Charm during the battle, as his Nail Arts only take half of a second to charge, unlike the Nailmasters who take about 2 seconds to charge. Sly himself is also the one who grants the Charm in the main game.

References

Великий гуру гвоздей Слай Gran Maestro d'Aculeo Sly Wielki Mędrzec Ostrza Sly