The idea behind the build is having more burst damage than the usual lich bane rabadons build. In this build, many weaknesses of Ezreal are corrected.

Items) Starting with spellthief-sheen-hextech gives Ezreal huge procs on his auto attacks and Qs with different timings. This means that he becomes very versatile and unpredictable. His Q will be overloaded with a lot of damage. The items themselves do not cost much, and will be really easy to obtain.

Next up is the catalyst. It gives Ezreal a tankier feeling, one that he really lacks without any hp-boosting items. After this, frost queen's claim simply gives too much utility in lane, and cc that Ezreal normally lacks. It also pays for itself, meaning that the build will be shorter by one item, and since this build is not that expensive, it also means hitting the highest point of the curve faster than others. After builting the hextech GPL item, he has another source of cc, that scales with ap at 35%, along with a boost to his waveclear. Finally, lich bane provides the final proc.

Luden's echo as a final item will give procs to non-auto abilities (W,E,R). This complements this build fantastically. Also, after obtaining rabadon's, all of Ezreal's items will get a huge percentage ap boost (lich, hextech GPL, luden's).

Ezreal becomes tankier, has crowd control, more burst, a lot of mana and mana regeneration and a faster burst curve! This makes this build practical for all elos!