I noticed that sunbeam allows you to to create multiple lines within a single turn. What's the maximum possible amount of sunbeam lines able to be within one turn? I'm interested solely in the maximum number of beams fired, be that by allies, glyph's of warding, simulacra, etc. However, all of the beams must be fired on one turn, not throughout a round.
For reference, the spell has a casting time of 1 action and states:
A beam of brilliant light flashes out from your hand in a 5-foot-wide, 60-foot-long line. Each creature in the line must make a Constitution saving throw. On a failed save, a creature takes 6d8 radiant damage and is blinded until your next turn. On a successful save, it takes half as much damage and isn't blinded by this spell. Undead and oozes have disadvantage on this saving throw.
You can create a new line of radiance as your action on any turn until the spell ends.
Rules
- Level 20 Character, any combination of multi-classing allowed
- Only official material published by WOTC in book form is allowed. No Unearthed Arcana
- Setup is allowed, including any magical items present in the Dungeon Master's Guide or any other source-book. Items only present in campaign books are not allowed.
- You may have 4 allies at level 20
- Simulacrum is allowed
- The allies and any simulacra are allowed to cast spells.
- One Epic Boon is allowed
- Anything dependent on RNG, such as the Wild Magic Table, is not allowed.
Best Answer
Infinite simulacra firing infinite beams with infinite readied actions
You are a Wizard who knows Wish, Simulacrum, and Sunbeam. For setup, you cast Simulacrum on yourself, then have your simulacrum cast Wish to wish for a simulacrum of you. Have the new simulacrum do likewise, and continue doing this until you have as many simulacra as you want. Each simulacrum readies a Sunbeam spell to be released on your signal. You give the signal, and an arbitrarily large number of sunbeams are fired.
(At some point, there won't be enough room for more simulacra within 6 light-seconds of you, so the signal will reach some of them on subsequent rounds, but if you have reached the point where relativity and speed-of-light delays are an issue, the shortcomings of D&D 5e's "physics engine" will be the least of your worries.)