Shieldmage Elder — ruling 1

If the ability is activated targeting a spell that becomes a permanent, it also prevents any damage from that permanent this turn.

Shieldmage Elder — ruling 2

You may tap any untapped permanents you control with the appropriate creature type (including this creature) to pay the cost of the ability, including creatures that haven't been under your control continuously since the beginning of your most recent turn.

Shieldmage Elder : règles, fonctionnement et interactions (MTG)

Shieldmage Elder is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Tap two untapped Clerics you control: Prevent all damage target creature would deal this turn. Tap two untapped Wizards you control: Prevent all damage target spell would deal this turn.

How it works : Shieldmage Elder

Original English text — Wizards of the Coast / Scryfall

#1October 4, 2004· Wizards of the Coast
If the ability is activated targeting a spell that becomes a permanent, it also prevents any damage from that permanent this turn.
No other card is named in this ruling.
#2October 4, 2004· Wizards of the Coast
You may tap any untapped permanents you control with the appropriate creature type (including this creature) to pay the cost of the ability, including creatures that haven't been under your control continuously since the beginning of your most recent turn.
No other card is named in this ruling.