MTGNexus

Hi, can I cast the elderspell to destroy enemy walkers even if I don't control any planeswalker?

Absolutely.

When card text simply says "Choose a __" you have to choose the relevant [object] when available, but it is not a requirement of casting the spell. If you have a planeswalker, you are required to choose it for getting counters, but it is not a requirement for casting the spell. All of the other effects (ie: destroying any number of planeswalkers) still happen.

Alternately, for context, if the card text says "target ___ you control", it would it require you to have the [object] to fulfill all required legal targets, which is part of casting a spell. Since this does not use the word target, and only "choose", it is not a targetting requirement, and thus not specifically necessary for the spell to be cast and resolve.

ah, great. Thanks for clearing that up. Gonna use this as a sideboard card.