Morello’s Evil Tome
Reducing healing has always been a powerful effect in Teamfight Tactics as it helps your team eliminate the opposing team’s carries. Therefore, items like Morello’s Evil Tome and Thornmail are commonly built. It wouldn’t be fun to be helpless against an enemy’s Draven just because you don’t have Morello’s Evil Tome to counter the healing from Bloodthirster. Thus, it’s perfectly normal for this item to be strong in Season 6.5.

However, what makes Morello’s Evil Tome so powerful right now is also due to the fact that Brawler units are becoming extremely popular, with many strong champions using this unit. With the addition of Sejuani and Rek’Sai, Brawler units are incredibly strong thanks to activating many traits – systems, so the counter approach named Morello’s Evil Tome has been continuously built. Moreover, new powerful units like Morgana, Renata, and Alistar are also very suitable for this item, making it more popular than before.
Thornmail
It’s unclear if Riot Games is showing favoritism, but in the current Season 6.5, many strong physical damage compositions are on the rise. Meanwhile, team comps revolving around magic damage seem to be extremely weak, particularly the Mage composition. This leads to Infinity Edge and other items that provide strong physical damage completely dominating and becoming a very powerful type of offensive item.

As a result, whether you want to or not, building Thornmail is almost mandatory in the current meta if you want to keep your tank champions alive to apply effects. In some cases, this item also needs to be built for melee carries like Tryndamere and Irelia to avoid being “burst” before reaching the enemy. Therefore, the advice here is to build Thornmail as early as possible, regardless of what composition you are playing.
Quicksilver
Although it does not provide damage, Quicksilver is becoming an indispensable tool for carries to survive and deal effective damage. Indeed, in Season 6.5, Riot has added or revamped too many champions that can apply strong crowd control, causing annoying effects such as Alistar, Vi, Syndra… And to allow carries to feel more comfortable dealing damage, Quicksilver is a necessary item, even if it means sacrificing an offensive item slot.

Additionally, the emergence of powerful melee carries like Irelia, Tryndamere… also significantly increases the value of Quicksilver. Due to the nature of melee champions, these units are very susceptible to getting caught in enemy crowd control while casting their abilities, losing a significant amount of damage. Quicksilver will solve this issue and prevent the aforementioned melee carries from being interrupted as frequently as before.