What's the longest a champion can continuously be invulnerable for?

Not to be confused with this question, I'm not asking about stasis and I'm interested in continuous application, not a simply chained one.

For how long can a champion be continuously immune to any damage directed at them (doesn't matter if they can or cannot be targeted)?

A valid sample combination:

• Kayle's ultimate
• Zhonya's Hourglass just before the former wears off

A sample invalid combination:

• Zhonya's Hourglass
• Kayle's ultimate

The latter is invalid because there is a small pocket of time during which the champion might theoretically take damage, since Kayle can't cast the ultimate on the champion under Zhonya's while it's active.

What's the longest such valid combination (in seconds, not by number of spells)?

Solution 1:

That would be 5.5 seconds for every champion and 13.5 seconds for Poppy.

Since you won't allow a small time window it works as follows:

For every champion: Kayle ultimate - 3 seconds
Stasis (Bard R, Lissandra R, Zhonya's Hourglass) - 2.5 Seconds

Now of course you'd have to time this absolutely perfectly and as you've mentioned slightly before kayle ultimate wears off.

Poppy can extend the invulnerability to 13 seconds with her ultimate but only from champions that aren't targeted by her ultimate.

Tryndamere can also add in his ultimate to a Zhonya's and Kayle ult. He doesn't really become immune to damage but he cannot die. He can extend the duration of his "unkillable" state to 10.5 seconds