going of without any legal targets

[GenioDeArena]

The card in question is Wickerbrough Elder, but I think the problem applyes to many more. Can I play an ability without a legal target? will it fizzle or it cant be played to begin with? how about the same situation but with spells instead of activated abilities? like (for exaple casting a counterspell with no other spell on the stack).

Thanks everybody

[dorsch]

You can activate an ability (or cast a spell) only if you have legal targets for each target the spell requires.