Doomcaliber/Thunder King Rai Oh vs Fiendish Chain

[icecreamsandwich]

Can I activate the effects of either Doomcaliber Knight or Thunder King Rai oh while they are Fiendish Chained?

[lolnopound]

Fiendish Chain doesn't stop effects from activating.

[CrazyCat]

Its not a "can I?" for Doomcal. Its mandatory; you do. They tribute themselves as costs, and thus Fiendish Chain holds no sway over what they do afterwards.