There are 4 Quests for the Tower of Rot Pre-Launch. The Bonus for completing all 4 is a Suffix: Defender of Qeynos.
Phase 1 Starts from May 14th and Ends July 7th. Phase 2 Starts from May 17th and Ends July 7th.

There are 3 Quests in the 1st Phase of the Pre-Launch:
From Whence They Came
Ether Too Near
Heads for the Hills

There is 1 Quest for the 2nd Phase of the Pre-Launch:
Beyond the Barrier