At mana value 3, it's not too expensive for what it does
You can either play it early on and slowly build counters on it by attacking throughout a few turns, or you can drop it when you have an army of elves in play and trigger it with just one attack
A fantastic addition to any deck that needs a few basic Forests to round it out
You can enable void in a variety of ways: by sacrificing permanents, warping creatures, trading in combat, or using removal
At this point, I'd suggest that you do an analysis of all the key local elements that might concern you, such as the local time zone, where you can go buy food, what time your event will take place, and by when you need your decklist submitted
1 Galadriel's Dismissal Protect Your Realm Single-target protection spells like Legolass Quick Reflexes are great for keeping one creature safe, but if youre looking to keep everything you control safe, Galadriels Dismissal is the best choice