Seden, the Elderstar

Hexproof
When Seden enters the battlefield and at the
beginning of your upkeep, place a Time counter
on Seden. As long as Seden has an even number
of Time counters on her, she gets +4/+4.
Whenever Seden attacks, she gains all other abilities
of creatures that are also attacking until end of turn.
If Seden would ever leave the battlefield, instead
return Seden to the battlefield.