Ker

Ker's Boss ability protects him from all destruction abilities except Fleeting, though not from death by damage, obliteration or bouncing.
Using the likes of Equip Armor on him is almost like casting EXP in a Can, but it also means when he is damaged, his attack drops.
Ker's attack-setting ability is generally disadvantagous, but this makes up for him being immune to destruction.
Ker does have the occasional advantage of being more resistant to attack reduction, such as The Sealing and Miasma Factory, as his attack will be raised again at the beginning of your turn.
Radioactive Battery works well on Ker, as his base attack is reset each turn.
His ability is due to his ATP being based on his HP because of his legendary sword, which is the Mugendai-Yaiba reforged.

Card History

Dec 28th, 2003: Card released in Clash of the Webcomics.
May 30th, 2005: Cost changed to 11 from 12.
Apr 18th, 2007: Cost changed to 10 from 11. Sac value changed to 12 from 13.
Sep 9th, 2007: Gained Boss.