Staggering Blow (Passive) - Nautilus' first basic attack against a target deals bonus physical damage and immobilizes the opponent briefly. Staggering Blow cannot trigger on the same target more than once every 12 seconds.
I wanted Nautilus' anchor to feel heavy and weighty, even if the player didn't build heavy attack damage items. Staggering Blow delivers a heavy hit to Nautilus' first attack against an enemy in a fight.
Since Staggering Blow's cooldown is on a per-unit basis, Nautilus can last-hit with greater ease and adds a bit of target selection gameplay while jungling or in a crowded team fight. Generally, melee doesn't have the luxury of choosing who it gets to targets in a fight. Staggering Blow gives additional incentives for the Nautilus player to try to reach and focus on other targets that may be harassing his team rather the closest target on him - as it guarantees that he has a minor crowd control effect up at all times.
Dredge Line - Nautilus throws his anchor forward. If he hits an enemy, he'll drag himself to his target and his target to him. If he hits terrain, he'll drag himself to the terrain and the cooldown is reduced.
Nautilus' Dredge Line is his primary initiation mechanic. Up close, it can be used to reset the position of various enemies. From afar, it can be used as a powerful movement ability or escape.
During the development of hookshot-style abilities, it rapidly became clear that the slower a champion is, the better hookshot would feel as a movement mechanic. For a tank, a delayed movement effect is ideal as the goal is to create an opening for the tank when two parties are at a standoff - rather than the required guaranteed movement a fighter has to have to close into the far back row of enemy champions to target squishy high-priority targets.
When two teams are at a standoff, the best initiators constantly probe at the enemy team, searching for vulnerable openings. Similar to Dark Binding and Bandage Toss, Dredge Line is intended to fulfill that purpose in a team stand-off
Titan's Wrath - Nautilus places a shield on himself that absorbs additional damage based on his maximum health. While the shield is active, Nautilus' attacks deal damage over time to units around him.
Wrath is soft-taunt mechanic for Nautilus. If Nautilus is the focus of enemy attacks, Wrath will defend him from incoming damage. However, if he's left alone, Nautilus can contribute heavy damage to the enemy team. Because it's a damage over time effect, Nautilus doesn't need attack speed to get the most benefit out of Titan's Wrath. Simply building any defensive item will contribute to Titan's Wrath's uptime, as armor and magic resist will reduce incoming damage to the shield, and raw health will amplify the raw shield strength.
One of the strongest downsides to a self-only shield is that it is effectively ignorable by the enemy team. Unless you are threatening enough so that you must be killed on sight, defensive shielded targets are generally ignored as there isn't a point to attacking him. Wrath allows Nautilus players to take advantage of this and punish enemy players for thinking he's ignorable. Over the course of a fight, Nautilus won't kill you quickly, but the damage will rapidly pile up the more time you give him.
Riptide - Nautilus slams the ground, causing the earth to ripple out in waves. Each wave deals damage and slows the targets hit. This slow decays over time. Multiple waves that hit the same target deal reduced damage.
Riptide grants Nautilus a strong area control effect. Because the rippling waves are delayed, Riptidecan act as a deterrent to enemies walking towards Nautilus. Using Riptide after Dredge Line can be a powerful soft-initiate. Enemies attempting to run away from Nautilus will run straight into the rapidly expanding waves, taking additional damage and refreshing the slow duration on them.
Many players know that the tank's fundamental role is to create openings for your team to attack. Intuitively, however, many players also understand that a tank is also there to prevent fighters/assassins from running into your squishy back-row and killing high priority targets. Riptide is designed to help hold the enemy front-line back or punishing them with more damage and slow if they choose to push forward.
Depth Charge (ultimate) - Nautilus launches a depth charge towards a target that picks up speed as it travels. This charge knocks up all enemies it encounters while traveling and explodes on impact, stunning the target and launching them into the air.
Depth Charge is Nautilus' fight-starter. Casting Depth Charge on back row targets will give them time to run, but will cause a great deal of chaos as the depth charge rips through the enemy team. Depth Charge can set up a guaranteed Dredge Line, ensuring Nautilus can charge into a battle with a clear shot and a stationary target.
Every tank benefits from having a fundamental initiation ability. Reliable initiation is one of the defining aspects that a tank needs to create opportunities for your team to engage and destroy the enemy. Depth Charge, combined with Dredge Line and Riptide can set up a trio of powerful effects that effectively force a fight to begin on your terms. Nautilus can put out a tremendous amount of raw disruption by chaining Depth Charge into Dredge Line into Riptide, forcing the enemy to respond or abandon the hapless enemies that have been stunned or slowed around Nautilus.