I am considering the potential implications of a house rule for Dungeons and Dragons 5th Edition. The rule is as follows:
- When a creature casts a spell of level 1 or higher with a casting time of 1 action or 1 bonus action, they follow the existing procedure for casting a spell, including choosing locations and targets, providing components, and so on. However, the spell does not take effect immediately. Instead, the spell's effects occur (for spells with instant duration) or begin (for spells with non-instant duration) at the beginning of that character's next turn. The spell slot and/or consumable components, if applicable, are consumed if and when the spell takes effect.
- If a creature takes damage after they begin casting a spell but before it takes effect, they must make a concentration check, using the existing rules. They must make this check for each spell they are casting. If the check is failed, the caster stops casting the spell and it will not take effect at the beginning of their next turn. The caster may also choose to stop casting the spell at any time before the beginning of their next turn.
- If a chosen target of the spell is no longer a valid target when the spell takes effect, the spell takes effect but does not affect that target.
How does this house rule interact with the existing rules as written? Does it produce any ambiguities or counterintuitive results?