Warlock

Overview
Warlock is a versatile spammy mage. Most of its spells have low cooldown but they come with a higher-than-average MP cost. However, thanks to its passive, Warlock can keep casting spells by paying HP even at 0 MP.

Warlock's main spells have bombastic names (Eldritch Blast and Eldritch Field) but they're actually simple damage spells. However, with the use of invocations, the Warlock can grant them additional effects such as extra power, range, debuffs or CC.

Warlock is also infamous for its ultimate, Eldritch Nightmare, which covers the immediate area in darkness. This large scale CC has a huge impact during team fights and it's the main reason Warlock is considered high tier. This ult is often memed as "click to win" because it's easy to use but gives a huge benefit.

Build
Warlock can be played as either a Mid Laner or as a Support.

As a Mid Laner, the Warlock's main concerns are his damage and his range. Therefore, Mid Warlock will usually level up Invocation up to Lv.2 and will spend the rest of his SP on other spells. This is because Lv.2 Invocation grants access to Power Invocation and Radius Invocation, which are the primary invocations a Mid Warlock needs. After gaining access to these invocations, it's best for a Mid Warlock to level up his spells to increase their damage.

On the other hand, for Support Warlock, damage is less important than CC. Therefore, a Support Warlock will level up Eldritch Blast and Eldritch Field only to Lv.1 and will invest the rest of his SP into Invocation and Eldritch Nightmare.

In the Novel
During middle school, Alex (Freezer) from the Leopards' second-string mained Warlock for both Mid and Support. He used Eldritch Nightmare to set up kills for Jennifer (ComboBreaker) and to give his team an edge in team fights. However, he became overly reliant on Warlock being high tier and, as a result, he neglected other classes. That came back to bite him when Yuel banned Warlock as a counter.